Schritt 1: Fundament der Lebensmittel-Lagerverwaltung (Pantry)

Backend (FastAPI + PostgreSQL): Chargen mit MHD, FEFO-Auslagern, Einheiten-Umrechnung (Stueck/g/ml + Packungen), Open-Food-Facts-Lookup mit lokalem Fallback, JWT-Auth mit Rollen (Admin/Nutzer), erster Admin beim Setup, Einkaufsliste, Ablaufwarnung, Lagerorte, pytest fuer FEFO. Web-UI (React/Vite): Login, Dashboard, Ein-/Auslagern, Produkte, Lagerorte, Benutzerverwaltung, Einkaufsliste - rollenabhaengig. Deploy: docker-compose + install.sh (Docker-Autoinstall, Secrets), README und Roadmap fuer Schritt 2 (iOS) und Schritt 3. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-07-22 09:14:14 +02:00
commit 639126468f
57 changed files with 3460 additions and 0 deletions
--- a/backend/.dockerignore
+++ b/backend/.dockerignore
@@ -0,0 +1,8 @@
+__pycache__/
+*.pyc
+.pytest_cache/
+.venv/
+venv/
+.env
+*.sqlite
+*.db
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@@ -0,0 +1,21 @@
+FROM python:3.12-slim
+
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1
+
+WORKDIR /app
+
+# System-Abhängigkeiten für psycopg2 & bcrypt
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends gcc libpq-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY app ./app
+COPY tests ./tests
+
+EXPOSE 8000
+
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]
--- a/backend/app/init.py
+++ b/backend/app/init.py
--- a/backend/app/config.py
+++ b/backend/app/config.py
@@ -0,0 +1,34 @@
+from functools import lru_cache
+
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(env_file=".env", extra="ignore")
+
+    # Database
+    database_url: str = "postgresql+psycopg2://pantry:pantry@localhost:5432/pantry"
+
+    # Auth / JWT
+    jwt_secret: str = "change-me-in-production"
+    jwt_algorithm: str = "HS256"
+    jwt_expire_minutes: int = 60 * 24 * 7  # 7 days
+
+    # First admin, created on startup if no users exist
+    admin_username: str = "admin"
+    admin_password: str = "changeme"
+
+    # Open Food Facts
+    off_base_url: str = "https://world.openfoodfacts.org"
+    off_timeout_seconds: float = 8.0
+
+    # Behaviour
+    expiry_warning_days_default: int = 7
+
+    # CORS (comma separated); "*" allows all
+    cors_origins: str = "*"
+
+
+@lru_cache
+def get_settings() -> Settings:
+    return Settings()
--- a/backend/app/crud.py
+++ b/backend/app/crud.py
@@ -0,0 +1,34 @@
+"""Kleine gemeinsame Helfer für Router."""
+
+from __future__ import annotations
+
+from fastapi import HTTPException, status
+from sqlalchemy.orm import Session
+
+from .models import Product
+from .schemas import ProductOut
+from .services.stock import current_stock
+
+
+def product_to_out(db: Session, product: Product) -> ProductOut:
+    out = ProductOut.model_validate(product)
+    out.stock = current_stock(db, product.id)
+    return out
+
+
+def resolve_product(
+    db: Session, product_id: int | None, barcode: str | None
+) -> Product:
+    """Findet ein Produkt per ID oder Barcode; wirft 404, wenn keins passt."""
+    product: Product | None = None
+    if product_id is not None:
+        product = db.get(Product, product_id)
+    elif barcode:
+        product = db.query(Product).filter(Product.barcode == barcode).first()
+    else:
+        raise HTTPException(
+            status.HTTP_400_BAD_REQUEST, "product_id oder barcode erforderlich"
+        )
+    if product is None:
+        raise HTTPException(status.HTTP_404_NOT_FOUND, "Produkt nicht gefunden")
+    return product
--- a/backend/app/database.py
+++ b/backend/app/database.py
@@ -0,0 +1,34 @@
+from collections.abc import Generator
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker
+
+from .config import get_settings
+
+settings = get_settings()
+
+# SQLite (used in tests) needs a special connect arg; Postgres does not.
+connect_args = {}
+if settings.database_url.startswith("sqlite"):
+    connect_args = {"check_same_thread": False}
+
+engine = create_engine(
+    settings.database_url,
+    connect_args=connect_args,
+    pool_pre_ping=True,
+    future=True,
+)
+
+SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, future=True)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+def get_db() -> Generator[Session, None, None]:
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
--- a/backend/app/deps.py
+++ b/backend/app/deps.py
@@ -0,0 +1,39 @@
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from sqlalchemy.orm import Session
+
+from .database import get_db
+from .models import Role, User
+from .security import decode_access_token
+
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="auth/login")
+
+_credentials_exc = HTTPException(
+    status_code=status.HTTP_401_UNAUTHORIZED,
+    detail="Ungültige oder abgelaufene Anmeldung",
+    headers={"WWW-Authenticate": "Bearer"},
+)
+
+
+def get_current_user(
+    token: str = Depends(oauth2_scheme), db: Session = Depends(get_db)
+) -> User:
+    payload = decode_access_token(token)
+    if payload is None:
+        raise _credentials_exc
+    username = payload.get("sub")
+    if not username:
+        raise _credentials_exc
+    user = db.query(User).filter(User.username == username).first()
+    if user is None:
+        raise _credentials_exc
+    return user
+
+
+def require_admin(current_user: User = Depends(get_current_user)) -> User:
+    if current_user.role != Role.admin:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Nur Administratoren dürfen diese Aktion ausführen",
+        )
+    return current_user
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -0,0 +1,61 @@
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+
+from .config import get_settings
+from .database import Base, SessionLocal, engine
+from .routers import (
+    auth,
+    groups,
+    locations,
+    products,
+    settings as settings_router,
+    stock,
+    users,
+    views,
+)
+from .seed import ensure_first_admin
+
+settings = get_settings()
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    # Tabellen anlegen (MVP: create_all statt Alembic-Migrationen).
+    Base.metadata.create_all(bind=engine)
+    db = SessionLocal()
+    try:
+        ensure_first_admin(db)
+    finally:
+        db.close()
+    yield
+
+
+app = FastAPI(title="Pantry – Lebensmittel-Lagerverwaltung", version="1.0.0", lifespan=lifespan)
+
+origins = ["*"] if settings.cors_origins.strip() == "*" else [
+    o.strip() for o in settings.cors_origins.split(",") if o.strip()
+]
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=origins,
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+
+@app.get("/health", tags=["meta"])
+def health() -> dict:
+    return {"status": "ok"}
+
+
+app.include_router(auth.router)
+app.include_router(users.router)
+app.include_router(products.router)
+app.include_router(stock.router)
+app.include_router(locations.router)
+app.include_router(groups.router)
+app.include_router(views.router)
+app.include_router(settings_router.router)
--- a/backend/app/models.py
+++ b/backend/app/models.py
@@ -0,0 +1,147 @@
+from __future__ import annotations
+
+import enum
+from datetime import date, datetime, timezone
+
+from sqlalchemy import (
+    Date,
+    DateTime,
+    Enum,
+    Float,
+    ForeignKey,
+    Integer,
+    String,
+    Text,
+    UniqueConstraint,
+)
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from .database import Base
+
+
+def _now() -> datetime:
+    return datetime.now(timezone.utc)
+
+
+class Role(str, enum.Enum):
+    admin = "admin"
+    user = "user"
+
+
+class BaseUnit(str, enum.Enum):
+    piece = "piece"
+    gram = "gram"
+    milliliter = "milliliter"
+
+
+class MovementType(str, enum.Enum):
+    in_ = "in"
+    out = "out"
+    adjust = "adjust"
+
+
+class User(Base):
+    __tablename__ = "users"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    username: Mapped[str] = mapped_column(String(64), unique=True, nullable=False)
+    password_hash: Mapped[str] = mapped_column(String(255), nullable=False)
+    role: Mapped[Role] = mapped_column(Enum(Role), nullable=False, default=Role.user)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)
+
+
+class Group(Base):
+    __tablename__ = "groups"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    name: Mapped[str] = mapped_column(String(120), unique=True, nullable=False)
+    # Group-level minimum stock is a Schritt-3 feature; column kept for forward-compat.
+    min_stock: Mapped[float | None] = mapped_column(Float, nullable=True)
+
+    products: Mapped[list[Product]] = relationship(back_populates="group")
+
+
+class Location(Base):
+    __tablename__ = "locations"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    name: Mapped[str] = mapped_column(String(120), nullable=False)
+    # Sub-locations (Regal/Fach) are a Schritt-3 feature; parent_id kept for forward-compat.
+    parent_id: Mapped[int | None] = mapped_column(
+        ForeignKey("locations.id", ondelete="SET NULL"), nullable=True
+    )
+
+
+class Product(Base):
+    __tablename__ = "products"
+    __table_args__ = (UniqueConstraint("barcode", name="uq_products_barcode"),)
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    barcode: Mapped[str | None] = mapped_column(String(64), nullable=True)
+    name: Mapped[str] = mapped_column(String(255), nullable=False)
+    brand: Mapped[str | None] = mapped_column(String(255), nullable=True)
+    image_url: Mapped[str | None] = mapped_column(String(1024), nullable=True)
+
+    base_unit: Mapped[BaseUnit] = mapped_column(
+        Enum(BaseUnit), nullable=False, default=BaseUnit.piece
+    )
+    # Number of base units contained in one package (e.g. 500 g per package).
+    package_size: Mapped[float | None] = mapped_column(Float, nullable=True)
+
+    group_id: Mapped[int | None] = mapped_column(
+        ForeignKey("groups.id", ondelete="SET NULL"), nullable=True
+    )
+    min_stock: Mapped[float | None] = mapped_column(Float, nullable=True)  # in base units
+
+    source: Mapped[str] = mapped_column(String(16), nullable=False, default="manual")
+    off_raw: Mapped[str | None] = mapped_column(Text, nullable=True)  # JSON blob from OFF
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)
+
+    group: Mapped[Group | None] = relationship(back_populates="products")
+    lots: Mapped[list[Lot]] = relationship(
+        back_populates="product", cascade="all, delete-orphan"
+    )
+
+
+class Lot(Base):
+    __tablename__ = "lots"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    product_id: Mapped[int] = mapped_column(
+        ForeignKey("products.id", ondelete="CASCADE"), nullable=False
+    )
+    quantity: Mapped[float] = mapped_column(Float, nullable=False)  # in base units
+    best_before: Mapped[date | None] = mapped_column(Date, nullable=True)
+    location_id: Mapped[int | None] = mapped_column(
+        ForeignKey("locations.id", ondelete="SET NULL"), nullable=True
+    )
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)
+
+    product: Mapped[Product] = relationship(back_populates="lots")
+
+
+class Movement(Base):
+    __tablename__ = "movements"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    product_id: Mapped[int] = mapped_column(
+        ForeignKey("products.id", ondelete="CASCADE"), nullable=False
+    )
+    lot_id: Mapped[int | None] = mapped_column(
+        ForeignKey("lots.id", ondelete="SET NULL"), nullable=True
+    )
+    user_id: Mapped[int | None] = mapped_column(
+        ForeignKey("users.id", ondelete="SET NULL"), nullable=True
+    )
+    type: Mapped[MovementType] = mapped_column(Enum(MovementType), nullable=False)
+    quantity: Mapped[float] = mapped_column(Float, nullable=False)  # in base units
+    unit_used: Mapped[str] = mapped_column(String(32), nullable=False)  # what user entered
+    note: Mapped[str | None] = mapped_column(String(255), nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)
+
+
+class Setting(Base):
+    __tablename__ = "settings"
+
+    key: Mapped[str] = mapped_column(String(64), primary_key=True)
+    value: Mapped[str] = mapped_column(String(255), nullable=False)
--- a/backend/app/off.py
+++ b/backend/app/off.py
@@ -0,0 +1,72 @@
+"""Open Food Facts Lookup-Client."""
+
+from __future__ import annotations
+
+import json
+
+import httpx
+
+from .config import get_settings
+
+settings = get_settings()
+
+
+def _guess_base_unit(quantity: str | None) -> str:
+    """Rät die Basiseinheit aus dem OFF-Feld 'quantity' (z.B. '500 g', '1 l')."""
+    if not quantity:
+        return "piece"
+    q = quantity.lower()
+    if "ml" in q or "cl" in q or "l" in q or "liter" in q:
+        return "milliliter"
+    if "kg" in q or " g" in q or "gramm" in q or q.strip().endswith("g"):
+        return "gram"
+    return "piece"
+
+
+def lookup_barcode(barcode: str) -> dict | None:
+    """Fragt Open Food Facts nach einem Barcode.
+
+    Gibt ein vorbefülltes Produkt-Dict zurück oder None, wenn nicht gefunden.
+    """
+    url = f"{settings.off_base_url}/api/v2/product/{barcode}.json"
+    try:
+        resp = httpx.get(
+            url,
+            timeout=settings.off_timeout_seconds,
+            headers={"User-Agent": "Pantry-Selfhosted/1.0 (github: pantry)"},
+        )
+    except httpx.HTTPError:
+        return None
+
+    if resp.status_code != 200:
+        return None
+
+    data = resp.json()
+    if data.get("status") != 1:
+        return None
+
+    product = data.get("product", {})
+    name = (
+        product.get("product_name_de")
+        or product.get("product_name")
+        or product.get("generic_name")
+        or ""
+    ).strip()
+    if not name:
+        return None
+
+    categories = product.get("categories") or ""
+    category_tags = product.get("categories_tags") or []
+
+    return {
+        "barcode": barcode,
+        "name": name,
+        "brand": (product.get("brands") or "").strip() or None,
+        "image_url": product.get("image_front_url") or product.get("image_url") or None,
+        "base_unit": _guess_base_unit(product.get("quantity")),
+        "quantity_text": product.get("quantity"),
+        "category_suggestion": categories.split(",")[0].strip() if categories else None,
+        "category_tags": category_tags,
+        "source": "off",
+        "off_raw": json.dumps(product)[:20000],
+    }
--- a/backend/app/routers/init.py
+++ b/backend/app/routers/init.py
--- a/backend/app/routers/auth.py
+++ b/backend/app/routers/auth.py
@@ -0,0 +1,30 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordRequestForm
+from sqlalchemy.orm import Session
+
+from ..database import get_db
+from ..deps import get_current_user
+from ..models import User
+from ..schemas import Token, UserOut
+from ..security import create_access_token, verify_password
+
+router = APIRouter(prefix="/auth", tags=["auth"])
+
+
+@router.post("/login", response_model=Token)
+def login(
+    form: OAuth2PasswordRequestForm = Depends(), db: Session = Depends(get_db)
+) -> Token:
+    user = db.query(User).filter(User.username == form.username).first()
+    if user is None or not verify_password(form.password, user.password_hash):
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Benutzername oder Passwort falsch",
+        )
+    token = create_access_token(subject=user.username, role=user.role.value)
+    return Token(access_token=token, role=user.role, username=user.username)
+
+
+@router.get("/me", response_model=UserOut)
+def me(current_user: User = Depends(get_current_user)) -> User:
+    return current_user
--- a/backend/app/routers/groups.py
+++ b/backend/app/routers/groups.py
@@ -0,0 +1,44 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from ..database import get_db
+from ..deps import get_current_user, require_admin
+from ..models import Group, User
+from ..schemas import GroupCreate, GroupOut
+
+router = APIRouter(prefix="/groups", tags=["groups"])
+
+
+@router.get("", response_model=list[GroupOut])
+def list_groups(
+    db: Session = Depends(get_db), _: User = Depends(get_current_user)
+) -> list[Group]:
+    return db.query(Group).order_by(Group.name).all()
+
+
+@router.post("", response_model=GroupOut, status_code=status.HTTP_201_CREATED)
+def create_group(
+    payload: GroupCreate,
+    db: Session = Depends(get_db),
+    _: User = Depends(require_admin),
+) -> Group:
+    if db.query(Group).filter(Group.name == payload.name).first():
+        raise HTTPException(status.HTTP_409_CONFLICT, "Gruppe existiert bereits")
+    group = Group(name=payload.name, min_stock=payload.min_stock)
+    db.add(group)
+    db.commit()
+    db.refresh(group)
+    return group
+
+
+@router.delete("/{group_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_group(
+    group_id: int,
+    db: Session = Depends(get_db),
+    _: User = Depends(require_admin),
+) -> None:
+    group = db.get(Group, group_id)
+    if group is None:
+        raise HTTPException(status.HTTP_404_NOT_FOUND, "Gruppe nicht gefunden")
+    db.delete(group)
+    db.commit()
--- a/backend/app/routers/locations.py
+++ b/backend/app/routers/locations.py
@@ -0,0 +1,42 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from ..database import get_db
+from ..deps import get_current_user, require_admin
+from ..models import Location, User
+from ..schemas import LocationCreate, LocationOut
+
+router = APIRouter(prefix="/locations", tags=["locations"])
+
+
+@router.get("", response_model=list[LocationOut])
+def list_locations(
+    db: Session = Depends(get_db), _: User = Depends(get_current_user)
+) -> list[Location]:
+    return db.query(Location).order_by(Location.name).all()
+
+
+@router.post("", response_model=LocationOut, status_code=status.HTTP_201_CREATED)
+def create_location(
+    payload: LocationCreate,
+    db: Session = Depends(get_db),
+    _: User = Depends(require_admin),
+) -> Location:
+    loc = Location(name=payload.name, parent_id=payload.parent_id)
+    db.add(loc)
+    db.commit()
+    db.refresh(loc)
+    return loc
+
+
+@router.delete("/{location_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_location(
+    location_id: int,
+    db: Session = Depends(get_db),
+    _: User = Depends(require_admin),
+) -> None:
+    loc = db.get(Location, location_id)
+    if loc is None:
+        raise HTTPException(status.HTTP_404_NOT_FOUND, "Lagerort nicht gefunden")
+    db.delete(loc)
+    db.commit()
--- a/backend/app/routers/products.py
+++ b/backend/app/routers/products.py
@@ -0,0 +1,125 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from ..crud import product_to_out
+from ..database import get_db
+from ..deps import get_current_user, require_admin
+from ..models import BaseUnit, Product, User
+from ..off import lookup_barcode
+from ..schemas import LookupResult, ProductCreate, ProductOut, ProductUpdate
+
+router = APIRouter(prefix="/products", tags=["products"])
+
+
+@router.get("", response_model=list[ProductOut])
+def list_products(
+    q: str | None = None,
+    db: Session = Depends(get_db),
+    _: User = Depends(get_current_user),
+) -> list[ProductOut]:
+    query = db.query(Product)
+    if q:
+        like = f"%{q}%"
+        query = query.filter(Product.name.ilike(like))
+    products = query.order_by(Product.name).all()
+    return [product_to_out(db, p) for p in products]
+
+
+@router.get("/lookup", response_model=LookupResult)
+def lookup(
+    barcode: str,
+    db: Session = Depends(get_db),
+    _: User = Depends(get_current_user),
+) -> LookupResult:
+    """Barcode: erst lokal, dann Open Food Facts. Nur Vorschlag, legt nichts an."""
+    existing = db.query(Product).filter(Product.barcode == barcode).first()
+    if existing:
+        return LookupResult(found=True, existing_product=product_to_out(db, existing))
+
+    suggestion = lookup_barcode(barcode)
+    if suggestion:
+        return LookupResult(found=True, suggestion=suggestion)
+    return LookupResult(found=False)
+
+
+@router.get("/{product_id}", response_model=ProductOut)
+def get_product(
+    product_id: int,
+    db: Session = Depends(get_db),
+    _: User = Depends(get_current_user),
+) -> ProductOut:
+    product = db.get(Product, product_id)
+    if product is None:
+        raise HTTPException(status.HTTP_404_NOT_FOUND, "Produkt nicht gefunden")
+    return product_to_out(db, product)
+
+
+@router.post("", response_model=ProductOut, status_code=status.HTTP_201_CREATED)
+def create_product(
+    payload: ProductCreate,
+    db: Session = Depends(get_db),
+    _: User = Depends(require_admin),
+) -> ProductOut:
+    if payload.barcode:
+        exists = db.query(Product).filter(Product.barcode == payload.barcode).first()
+        if exists:
+            raise HTTPException(
+                status.HTTP_409_CONFLICT, "Ein Produkt mit diesem Barcode existiert bereits"
+            )
+    product = Product(
+        barcode=payload.barcode or None,
+        name=payload.name,
+        brand=payload.brand,
+        image_url=payload.image_url,
+        base_unit=payload.base_unit,
+        package_size=payload.package_size,
+        group_id=payload.group_id,
+        min_stock=payload.min_stock,
+        source="manual",
+    )
+    db.add(product)
+    db.commit()
+    db.refresh(product)
+    return product_to_out(db, product)
+
+
+@router.patch("/{product_id}", response_model=ProductOut)
+def update_product(
+    product_id: int,
+    payload: ProductUpdate,
+    db: Session = Depends(get_db),
+    _: User = Depends(require_admin),
+) -> ProductOut:
+    product = db.get(Product, product_id)
+    if product is None:
+        raise HTTPException(status.HTTP_404_NOT_FOUND, "Produkt nicht gefunden")
+
+    data = payload.model_dump(exclude_unset=True)
+    if "barcode" in data and data["barcode"]:
+        clash = (
+            db.query(Product)
+            .filter(Product.barcode == data["barcode"], Product.id != product_id)
+            .first()
+        )
+        if clash:
+            raise HTTPException(
+                status.HTTP_409_CONFLICT, "Ein anderes Produkt hat diesen Barcode bereits"
+            )
+    for field, value in data.items():
+        setattr(product, field, value)
+    db.commit()
+    db.refresh(product)
+    return product_to_out(db, product)
+
+
+@router.delete("/{product_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_product(
+    product_id: int,
+    db: Session = Depends(get_db),
+    _: User = Depends(require_admin),
+) -> None:
+    product = db.get(Product, product_id)
+    if product is None:
+        raise HTTPException(status.HTTP_404_NOT_FOUND, "Produkt nicht gefunden")
+    db.delete(product)
+    db.commit()
--- a/backend/app/routers/settings.py
+++ b/backend/app/routers/settings.py
@@ -0,0 +1,49 @@
+from fastapi import APIRouter, Depends
+from sqlalchemy.orm import Session
+
+from ..config import get_settings
+from ..database import get_db
+from ..deps import get_current_user, require_admin
+from ..models import Setting, User
+from ..schemas import SettingOut
+
+router = APIRouter(prefix="/settings", tags=["settings"])
+
+EXPIRY_WARNING_KEY = "expiry_warning_days"
+
+
+def get_expiry_warning_days(db: Session) -> int:
+    row = db.get(Setting, EXPIRY_WARNING_KEY)
+    if row is None:
+        return get_settings().expiry_warning_days_default
+    try:
+        return int(row.value)
+    except ValueError:
+        return get_settings().expiry_warning_days_default
+
+
+@router.get("", response_model=list[SettingOut])
+def list_settings(
+    db: Session = Depends(get_db), _: User = Depends(get_current_user)
+) -> list[SettingOut]:
+    rows = db.query(Setting).all()
+    known = {r.key: r.value for r in rows}
+    known.setdefault(EXPIRY_WARNING_KEY, str(get_expiry_warning_days(db)))
+    return [SettingOut(key=k, value=v) for k, v in known.items()]
+
+
+@router.put("/{key}", response_model=SettingOut)
+def set_setting(
+    key: str,
+    value: str,
+    db: Session = Depends(get_db),
+    _: User = Depends(require_admin),
+) -> SettingOut:
+    row = db.get(Setting, key)
+    if row is None:
+        row = Setting(key=key, value=value)
+        db.add(row)
+    else:
+        row.value = value
+    db.commit()
+    return SettingOut(key=key, value=value)
--- a/backend/app/routers/stock.py
+++ b/backend/app/routers/stock.py
@@ -0,0 +1,83 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from ..crud import resolve_product
+from ..database import get_db
+from ..deps import get_current_user
+from ..models import Lot, User
+from ..schemas import (
+    CheckInRequest,
+    CheckInResponse,
+    CheckOutRequest,
+    CheckOutResponse,
+    LotOut,
+)
+from ..services.stock import StockError, check_in, check_out, current_stock
+from ..services.units import UnitError
+
+router = APIRouter(tags=["stock"])
+
+
+@router.post("/stock/checkin", response_model=CheckInResponse)
+def stock_checkin(
+    payload: CheckInRequest,
+    db: Session = Depends(get_db),
+    user: User = Depends(get_current_user),
+) -> CheckInResponse:
+    product = resolve_product(db, payload.product_id, payload.barcode)
+    try:
+        lot = check_in(
+            db,
+            product=product,
+            quantity=payload.quantity,
+            unit=payload.unit,
+            best_before=payload.best_before,
+            location_id=payload.location_id,
+            user=user,
+            note=payload.note,
+        )
+    except UnitError as exc:
+        raise HTTPException(status.HTTP_400_BAD_REQUEST, str(exc)) from exc
+    db.commit()
+    db.refresh(lot)
+    return CheckInResponse(
+        lot=LotOut.model_validate(lot), product_stock=current_stock(db, product.id)
+    )
+
+
+@router.post("/stock/checkout", response_model=CheckOutResponse)
+def stock_checkout(
+    payload: CheckOutRequest,
+    db: Session = Depends(get_db),
+    user: User = Depends(get_current_user),
+) -> CheckOutResponse:
+    product = resolve_product(db, payload.product_id, payload.barcode)
+    try:
+        affected = check_out(
+            db,
+            product=product,
+            quantity=payload.quantity,
+            unit=payload.unit,
+            user=user,
+            note=payload.note,
+        )
+    except UnitError as exc:
+        raise HTTPException(status.HTTP_400_BAD_REQUEST, str(exc)) from exc
+    except StockError as exc:
+        raise HTTPException(status.HTTP_409_CONFLICT, str(exc)) from exc
+    db.commit()
+    return CheckOutResponse(
+        affected_lots=affected, product_stock=current_stock(db, product.id)
+    )
+
+
+@router.get("/lots", response_model=list[LotOut])
+def list_lots(
+    product_id: int | None = None,
+    db: Session = Depends(get_db),
+    _: User = Depends(get_current_user),
+) -> list[Lot]:
+    query = db.query(Lot)
+    if product_id is not None:
+        query = query.filter(Lot.product_id == product_id)
+    return query.order_by(Lot.best_before.is_(None), Lot.best_before).all()
--- a/backend/app/routers/users.py
+++ b/backend/app/routers/users.py
@@ -0,0 +1,68 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from ..database import get_db
+from ..deps import require_admin
+from ..models import Role, User
+from ..schemas import UserCreate, UserOut, UserUpdate
+from ..security import hash_password
+
+router = APIRouter(prefix="/users", tags=["users"], dependencies=[Depends(require_admin)])
+
+
+@router.get("", response_model=list[UserOut])
+def list_users(db: Session = Depends(get_db)) -> list[User]:
+    return db.query(User).order_by(User.username).all()
+
+
+@router.post("", response_model=UserOut, status_code=status.HTTP_201_CREATED)
+def create_user(payload: UserCreate, db: Session = Depends(get_db)) -> User:
+    if db.query(User).filter(User.username == payload.username).first():
+        raise HTTPException(status.HTTP_409_CONFLICT, "Benutzername existiert bereits")
+    user = User(
+        username=payload.username,
+        password_hash=hash_password(payload.password),
+        role=payload.role,
+    )
+    db.add(user)
+    db.commit()
+    db.refresh(user)
+    return user
+
+
+@router.patch("/{user_id}", response_model=UserOut)
+def update_user(
+    user_id: int, payload: UserUpdate, db: Session = Depends(get_db)
+) -> User:
+    user = db.get(User, user_id)
+    if user is None:
+        raise HTTPException(status.HTTP_404_NOT_FOUND, "Benutzer nicht gefunden")
+    if payload.password is not None:
+        user.password_hash = hash_password(payload.password)
+    if payload.role is not None:
+        user.role = payload.role
+    db.commit()
+    db.refresh(user)
+    return user
+
+
+@router.delete("/{user_id}", status_code=status.HTTP_204_NO_CONTENT)
+def delete_user(
+    user_id: int,
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(require_admin),
+) -> None:
+    user = db.get(User, user_id)
+    if user is None:
+        raise HTTPException(status.HTTP_404_NOT_FOUND, "Benutzer nicht gefunden")
+    if user.id == current_admin.id:
+        raise HTTPException(status.HTTP_400_BAD_REQUEST, "Du kannst dich nicht selbst löschen")
+    # Verhindere das Löschen des letzten Admins.
+    if user.role == Role.admin:
+        admin_count = db.query(User).filter(User.role == Role.admin).count()
+        if admin_count <= 1:
+            raise HTTPException(
+                status.HTTP_400_BAD_REQUEST, "Der letzte Administrator kann nicht gelöscht werden"
+            )
+    db.delete(user)
+    db.commit()
--- a/backend/app/routers/views.py
+++ b/backend/app/routers/views.py
@@ -0,0 +1,76 @@
+from datetime import date, timedelta
+
+from fastapi import APIRouter, Depends
+from sqlalchemy.orm import Session
+
+from ..database import get_db
+from ..deps import get_current_user
+from ..models import Lot, Product, User
+from ..schemas import ExpiringItem, ShoppingItem
+from ..services.stock import current_stock
+from .settings import get_expiry_warning_days
+
+router = APIRouter(tags=["views"])
+
+
+@router.get("/shopping-list", response_model=list[ShoppingItem])
+def shopping_list(
+    db: Session = Depends(get_db), _: User = Depends(get_current_user)
+) -> list[ShoppingItem]:
+    """Produkte, deren Bestand unter dem Mindestbestand liegt."""
+    items: list[ShoppingItem] = []
+    products = (
+        db.query(Product)
+        .filter(Product.min_stock.isnot(None), Product.min_stock > 0)
+        .all()
+    )
+    for product in products:
+        stock = current_stock(db, product.id)
+        if stock < product.min_stock:
+            items.append(
+                ShoppingItem(
+                    product_id=product.id,
+                    name=product.name,
+                    base_unit=product.base_unit,
+                    stock=stock,
+                    min_stock=product.min_stock,
+                    deficit=product.min_stock - stock,
+                )
+            )
+    items.sort(key=lambda i: i.deficit, reverse=True)
+    return items
+
+
+@router.get("/expiring", response_model=list[ExpiringItem])
+def expiring(
+    days: int | None = None,
+    db: Session = Depends(get_db),
+    _: User = Depends(get_current_user),
+) -> list[ExpiringItem]:
+    """Chargen, die innerhalb der Warnfrist ablaufen (oder schon abgelaufen sind)."""
+    if days is None:
+        days = get_expiry_warning_days(db)
+    today = date.today()
+    threshold = today + timedelta(days=days)
+
+    lots = (
+        db.query(Lot)
+        .filter(Lot.best_before.isnot(None), Lot.best_before <= threshold, Lot.quantity > 0)
+        .order_by(Lot.best_before)
+        .all()
+    )
+    result: list[ExpiringItem] = []
+    for lot in lots:
+        product = lot.product
+        result.append(
+            ExpiringItem(
+                lot_id=lot.id,
+                product_id=product.id,
+                product_name=product.name,
+                quantity=lot.quantity,
+                base_unit=product.base_unit,
+                best_before=lot.best_before,
+                days_left=(lot.best_before - today).days,
+            )
+        )
+    return result
--- a/backend/app/schemas.py
+++ b/backend/app/schemas.py
@@ -0,0 +1,174 @@
+from __future__ import annotations
+
+from datetime import date, datetime
+
+from pydantic import BaseModel, ConfigDict, Field
+
+from .models import BaseUnit, Role
+
+
+# ---- Auth / Users ----
+class Token(BaseModel):
+    access_token: str
+    token_type: str = "bearer"
+    role: Role
+    username: str
+
+
+class UserOut(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+    id: int
+    username: str
+    role: Role
+    created_at: datetime
+
+
+class UserCreate(BaseModel):
+    username: str = Field(min_length=1, max_length=64)
+    password: str = Field(min_length=4, max_length=255)
+    role: Role = Role.user
+
+
+class UserUpdate(BaseModel):
+    password: str | None = Field(default=None, min_length=4, max_length=255)
+    role: Role | None = None
+
+
+# ---- Groups ----
+class GroupOut(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+    id: int
+    name: str
+    min_stock: float | None = None
+
+
+class GroupCreate(BaseModel):
+    name: str = Field(min_length=1, max_length=120)
+    min_stock: float | None = None
+
+
+# ---- Locations ----
+class LocationOut(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+    id: int
+    name: str
+    parent_id: int | None = None
+
+
+class LocationCreate(BaseModel):
+    name: str = Field(min_length=1, max_length=120)
+    parent_id: int | None = None
+
+
+# ---- Products ----
+class ProductBase(BaseModel):
+    barcode: str | None = None
+    name: str = Field(min_length=1, max_length=255)
+    brand: str | None = None
+    image_url: str | None = None
+    base_unit: BaseUnit = BaseUnit.piece
+    package_size: float | None = Field(default=None, gt=0)
+    group_id: int | None = None
+    min_stock: float | None = Field(default=None, ge=0)
+
+
+class ProductCreate(ProductBase):
+    pass
+
+
+class ProductUpdate(BaseModel):
+    barcode: str | None = None
+    name: str | None = Field(default=None, min_length=1, max_length=255)
+    brand: str | None = None
+    image_url: str | None = None
+    base_unit: BaseUnit | None = None
+    package_size: float | None = Field(default=None, gt=0)
+    group_id: int | None = None
+    min_stock: float | None = Field(default=None, ge=0)
+
+
+class ProductOut(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+    id: int
+    barcode: str | None
+    name: str
+    brand: str | None
+    image_url: str | None
+    base_unit: BaseUnit
+    package_size: float | None
+    group_id: int | None
+    min_stock: float | None
+    source: str
+    created_at: datetime
+    # angereichert:
+    stock: float = 0.0
+
+
+class LookupResult(BaseModel):
+    found: bool
+    existing_product: ProductOut | None = None
+    suggestion: dict | None = None
+
+
+# ---- Stock movements ----
+class CheckInRequest(BaseModel):
+    product_id: int | None = None
+    barcode: str | None = None
+    quantity: float = Field(gt=0)
+    unit: str
+    best_before: date | None = None
+    location_id: int | None = None
+    note: str | None = None
+
+
+class CheckOutRequest(BaseModel):
+    product_id: int | None = None
+    barcode: str | None = None
+    quantity: float = Field(gt=0)
+    unit: str
+    note: str | None = None
+
+
+class LotOut(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+    id: int
+    product_id: int
+    quantity: float
+    best_before: date | None
+    location_id: int | None
+    created_at: datetime
+
+
+class CheckInResponse(BaseModel):
+    lot: LotOut
+    product_stock: float
+
+
+class CheckOutResponse(BaseModel):
+    affected_lots: list[dict]
+    product_stock: float
+
+
+# ---- Views ----
+class ShoppingItem(BaseModel):
+    product_id: int
+    name: str
+    base_unit: BaseUnit
+    stock: float
+    min_stock: float
+    deficit: float
+
+
+class ExpiringItem(BaseModel):
+    lot_id: int
+    product_id: int
+    product_name: str
+    quantity: float
+    base_unit: BaseUnit
+    best_before: date
+    days_left: int
+
+
+class SettingOut(BaseModel):
+    key: str
+    value: str
--- a/backend/app/security.py
+++ b/backend/app/security.py
@@ -0,0 +1,31 @@
+from datetime import datetime, timedelta, timezone
+
+from jose import JWTError, jwt
+from passlib.context import CryptContext
+
+from .config import get_settings
+
+settings = get_settings()
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+
+def hash_password(password: str) -> str:
+    return pwd_context.hash(password)
+
+
+def verify_password(password: str, password_hash: str) -> bool:
+    return pwd_context.verify(password, password_hash)
+
+
+def create_access_token(subject: str, role: str) -> str:
+    expire = datetime.now(timezone.utc) + timedelta(minutes=settings.jwt_expire_minutes)
+    payload = {"sub": subject, "role": role, "exp": expire}
+    return jwt.encode(payload, settings.jwt_secret, algorithm=settings.jwt_algorithm)
+
+
+def decode_access_token(token: str) -> dict | None:
+    try:
+        return jwt.decode(token, settings.jwt_secret, algorithms=[settings.jwt_algorithm])
+    except JWTError:
+        return None
--- a/backend/app/seed.py
+++ b/backend/app/seed.py
@@ -0,0 +1,21 @@
+"""Erstellt beim ersten Start einen Admin-Benutzer, falls noch keiner existiert."""
+
+from sqlalchemy.orm import Session
+
+from .config import get_settings
+from .models import Role, User
+from .security import hash_password
+
+
+def ensure_first_admin(db: Session) -> None:
+    settings = get_settings()
+    has_users = db.query(User).first() is not None
+    if has_users:
+        return
+    admin = User(
+        username=settings.admin_username,
+        password_hash=hash_password(settings.admin_password),
+        role=Role.admin,
+    )
+    db.add(admin)
+    db.commit()
--- a/backend/app/services/init.py
+++ b/backend/app/services/init.py
--- a/backend/app/services/stock.py
+++ b/backend/app/services/stock.py
@@ -0,0 +1,125 @@
+"""Chargen-Logik: Einlagern erzeugt Lots, Auslagern bucht per FEFO ab."""
+
+from __future__ import annotations
+
+from datetime import date
+
+from sqlalchemy import asc
+from sqlalchemy.orm import Session
+
+from ..models import Lot, Movement, MovementType, Product, User
+from .units import to_base_quantity
+
+
+class StockError(ValueError):
+    """Fachlicher Fehler beim Ein-/Auslagern (z.B. zu wenig Bestand)."""
+
+
+def current_stock(db: Session, product_id: int) -> float:
+    """Summe der Lot-Mengen eines Produkts (in Basiseinheiten)."""
+    total = (
+        db.query(Lot).with_entities(Lot.quantity).filter(Lot.product_id == product_id).all()
+    )
+    return float(sum(q for (q,) in total))
+
+
+def check_in(
+    db: Session,
+    product: Product,
+    quantity: float,
+    unit: str,
+    best_before: date | None,
+    location_id: int | None,
+    user: User | None,
+    note: str | None = None,
+) -> Lot:
+    """Legt eine neue Charge an und protokolliert die Bewegung."""
+    quantity_base = to_base_quantity(product, quantity, unit)
+
+    lot = Lot(
+        product_id=product.id,
+        quantity=quantity_base,
+        best_before=best_before,
+        location_id=location_id,
+    )
+    db.add(lot)
+    db.flush()  # lot.id verfügbar machen
+
+    db.add(
+        Movement(
+            product_id=product.id,
+            lot_id=lot.id,
+            user_id=user.id if user else None,
+            type=MovementType.in_,
+            quantity=quantity_base,
+            unit_used=unit,
+            note=note,
+        )
+    )
+    return lot
+
+
+def _fefo_lots(db: Session, product_id: int) -> list[Lot]:
+    """Lots eines Produkts, sortiert nach Ablaufdatum (NULL zuletzt), dann Alter."""
+    lots = (
+        db.query(Lot)
+        .filter(Lot.product_id == product_id, Lot.quantity > 0)
+        .order_by(asc(Lot.created_at))
+        .all()
+    )
+    # NULL-best_before ans Ende (nach Datum aufsteigend). In Python sortieren, damit
+    # es über SQLite und Postgres identisch funktioniert.
+    return sorted(
+        lots,
+        key=lambda lot: (lot.best_before is None, lot.best_before or date.max, lot.id),
+    )
+
+
+def check_out(
+    db: Session,
+    product: Product,
+    quantity: float,
+    unit: str,
+    user: User | None,
+    note: str | None = None,
+) -> list[dict]:
+    """Bucht ``quantity`` (in ``unit``) per FEFO von den Chargen ab.
+
+    Gibt die Liste der betroffenen Chargen mit abgebuchter Menge zurück.
+    Wirft StockError, wenn der Gesamtbestand nicht ausreicht.
+    """
+    needed = to_base_quantity(product, quantity, unit)
+    available = current_stock(db, product.id)
+    if needed > available + 1e-9:
+        raise StockError(
+            f"Nicht genug Bestand: benötigt {needed:g}, verfügbar {available:g} "
+            f"{product.base_unit.value}"
+        )
+
+    affected: list[dict] = []
+    remaining = needed
+    for lot in _fefo_lots(db, product.id):
+        if remaining <= 1e-9:
+            break
+        take = min(lot.quantity, remaining)
+        lot.quantity -= take
+        remaining -= take
+
+        db.add(
+            Movement(
+                product_id=product.id,
+                lot_id=lot.id,
+                user_id=user.id if user else None,
+                type=MovementType.out,
+                quantity=take,
+                unit_used=unit,
+                note=note,
+            )
+        )
+        affected.append({"lot_id": lot.id, "quantity": take})
+
+        # Leere Charge entfernen, damit das "MHD-Array" sauber bleibt.
+        if lot.quantity <= 1e-9:
+            db.delete(lot)
+
+    return affected
--- a/backend/app/services/units.py
+++ b/backend/app/services/units.py
@@ -0,0 +1,64 @@
+"""Einheiten-Umrechnung.
+
+Der Bestand einer Charge (Lot) wird immer in der Basiseinheit des Produkts
+gespeichert (Stück, Gramm oder Milliliter). Nutzer geben Mengen entweder in der
+Basiseinheit oder in "Packungen" (package) an. Eine Packung entspricht
+``product.package_size`` Basiseinheiten.
+"""
+
+from __future__ import annotations
+
+from ..models import BaseUnit, Product
+
+# Aliase, die als "Basiseinheit" akzeptiert werden.
+_BASE_ALIASES: dict[str, BaseUnit] = {
+    "piece": BaseUnit.piece,
+    "pieces": BaseUnit.piece,
+    "stück": BaseUnit.piece,
+    "stueck": BaseUnit.piece,
+    "st": BaseUnit.piece,
+    "g": BaseUnit.gram,
+    "gram": BaseUnit.gram,
+    "gramm": BaseUnit.gram,
+    "ml": BaseUnit.milliliter,
+    "milliliter": BaseUnit.milliliter,
+}
+
+PACKAGE_UNITS = {"package", "packung", "pkg", "pack"}
+
+
+class UnitError(ValueError):
+    """Wird geworfen, wenn eine Einheit nicht zum Produkt passt."""
+
+
+def to_base_quantity(product: Product, quantity: float, unit: str) -> float:
+    """Rechnet eine vom Nutzer angegebene Menge in Basiseinheiten um."""
+    if quantity <= 0:
+        raise UnitError("Menge muss größer als 0 sein")
+
+    unit_norm = unit.strip().lower()
+
+    if unit_norm in PACKAGE_UNITS:
+        if not product.package_size or product.package_size <= 0:
+            raise UnitError(
+                "Für dieses Produkt ist keine Packungsgröße hinterlegt, "
+                "Packungen können nicht umgerechnet werden"
+            )
+        return quantity * product.package_size
+
+    mapped = _BASE_ALIASES.get(unit_norm)
+    if mapped is None:
+        raise UnitError(f"Unbekannte Einheit: {unit}")
+    if mapped != product.base_unit:
+        raise UnitError(
+            f"Einheit '{unit}' passt nicht zur Basiseinheit "
+            f"'{product.base_unit.value}' des Produkts"
+        )
+    return float(quantity)
+
+
+def base_to_packages(product: Product, quantity_base: float) -> float | None:
+    """Rechnet Basiseinheiten in (ggf. gebrochene) Packungen um, falls möglich."""
+    if not product.package_size or product.package_size <= 0:
+        return None
+    return quantity_base / product.package_size
--- a/backend/requirements.txt
+++ b/backend/requirements.txt
@@ -0,0 +1,12 @@
+fastapi==0.115.6
+uvicorn[standard]==0.34.0
+SQLAlchemy==2.0.36
+psycopg2-binary==2.9.10
+pydantic==2.10.4
+pydantic-settings==2.7.1
+python-jose[cryptography]==3.3.0
+passlib[bcrypt]==1.7.4
+bcrypt==4.2.1
+httpx==0.28.1
+python-dateutil==2.9.0.post0
+pytest==8.3.4
--- a/backend/tests/conftest.py
+++ b/backend/tests/conftest.py
@@ -0,0 +1,36 @@
+import pytest
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy.pool import StaticPool
+
+from app.database import Base
+from app.models import BaseUnit, Product
+
+
+@pytest.fixture()
+def db():
+    engine = create_engine(
+        "sqlite://",
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,
+    )
+    Base.metadata.create_all(bind=engine)
+    TestingSession = sessionmaker(bind=engine, autoflush=False, autocommit=False)
+    session = TestingSession()
+    try:
+        yield session
+    finally:
+        session.close()
+        engine.dispose()
+
+
+@pytest.fixture()
+def rice(db):
+    """Produkt mit Basiseinheit Gramm und 500 g pro Packung."""
+    product = Product(
+        name="Basmati-Reis", base_unit=BaseUnit.gram, package_size=500, source="manual"
+    )
+    db.add(product)
+    db.commit()
+    db.refresh(product)
+    return product
--- a/backend/tests/test_fefo.py
+++ b/backend/tests/test_fefo.py
@@ -0,0 +1,81 @@
+from datetime import date, timedelta
+
+import pytest
+
+from app.services.stock import StockError, check_in, check_out, current_stock
+
+
+def _checkin(db, product, qty, unit, best_before=None):
+    lot = check_in(db, product, qty, unit, best_before, None, None)
+    db.commit()
+    return lot
+
+
+def test_checkin_creates_lot_in_base_units(db, rice):
+    _checkin(db, rice, 3, "package")  # 1500 g
+    assert current_stock(db, rice.id) == 1500
+
+
+def test_checkout_partial_amount(db, rice):
+    _checkin(db, rice, 3, "package")  # 1500 g
+    check_out(db, rice, 200, "g", None)
+    db.commit()
+    assert current_stock(db, rice.id) == 1300
+
+
+def test_fefo_takes_earliest_expiry_first(db, rice):
+    soon = date.today() + timedelta(days=5)
+    later = date.today() + timedelta(days=60)
+    # Zuerst die später ablaufende Charge einlagern ...
+    _checkin(db, rice, 500, "g", best_before=later)
+    # ... dann die früher ablaufende.
+    _checkin(db, rice, 500, "g", best_before=soon)
+
+    check_out(db, rice, 400, "g", None)
+    db.commit()
+
+    # Die früh ablaufende Charge (soon) muss zuerst reduziert worden sein.
+    from app.models import Lot
+
+    lots = {l.best_before: l.quantity for l in db.query(Lot).all()}
+    assert lots[soon] == 100
+    assert lots[later] == 500
+
+
+def test_fefo_spans_multiple_lots_and_removes_empty(db, rice):
+    soon = date.today() + timedelta(days=5)
+    later = date.today() + timedelta(days=60)
+    _checkin(db, rice, 500, "g", best_before=soon)
+    _checkin(db, rice, 500, "g", best_before=later)
+
+    check_out(db, rice, 700, "g", None)  # 500 (soon) + 200 (later)
+    db.commit()
+
+    from app.models import Lot
+
+    lots = db.query(Lot).all()
+    assert len(lots) == 1  # leere soon-Charge entfernt
+    assert lots[0].best_before == later
+    assert lots[0].quantity == 300
+
+
+def test_null_best_before_is_last(db, rice):
+    dated = date.today() + timedelta(days=30)
+    _checkin(db, rice, 300, "g", best_before=None)
+    _checkin(db, rice, 300, "g", best_before=dated)
+
+    check_out(db, rice, 300, "g", None)
+    db.commit()
+
+    from app.models import Lot
+
+    remaining = db.query(Lot).all()
+    # Die datierte Charge wird zuerst genommen, die NULL-Charge bleibt.
+    assert len(remaining) == 1
+    assert remaining[0].best_before is None
+
+
+def test_checkout_more_than_available_raises(db, rice):
+    _checkin(db, rice, 100, "g")
+    with pytest.raises(StockError):
+        check_out(db, rice, 200, "g", None)
--- a/backend/tests/test_units.py
+++ b/backend/tests/test_units.py
@@ -0,0 +1,37 @@
+import pytest
+
+from app.models import BaseUnit, Product
+from app.services.units import UnitError, base_to_packages, to_base_quantity
+
+
+def test_base_unit_passthrough(rice):
+    assert to_base_quantity(rice, 200, "g") == 200
+    assert to_base_quantity(rice, 200, "gramm") == 200
+
+
+def test_package_conversion(rice):
+    # 3 Packungen * 500 g = 1500 g
+    assert to_base_quantity(rice, 3, "package") == 1500
+    assert to_base_quantity(rice, 2, "packung") == 1000
+
+
+def test_wrong_unit_rejected(rice):
+    with pytest.raises(UnitError):
+        to_base_quantity(rice, 1, "ml")
+
+
+def test_package_without_size_rejected():
+    product = Product(name="Ei", base_unit=BaseUnit.piece, package_size=None)
+    with pytest.raises(UnitError):
+        to_base_quantity(product, 1, "package")
+
+
+def test_non_positive_quantity_rejected(rice):
+    with pytest.raises(UnitError):
+        to_base_quantity(rice, 0, "g")
+
+
+def test_base_to_packages(rice):
+    assert base_to_packages(rice, 1500) == 3
+    product = Product(name="Ei", base_unit=BaseUnit.piece, package_size=None)
+    assert base_to_packages(product, 10) is None