Web-UI: professionelles Redesign (Icons statt Emojis) + neue Features

Design:
- Neues Icon-Set (Inline-SVG, Feather-Stil), keine Emojis mehr
- Kohaerentes Design-System (Sidebar-Layout, Palette, Spacing, Light/Dark)
- Alle Seiten ueberarbeitet (Login, Dashboard, Produkte, Formular, Ein-/Auslagern,
  Lagerorte, Benutzer, Einkaufsliste)

Neue Features:
- Gruppen-Verwaltung (anlegen/bearbeiten/loeschen, Produktzahl + Bestand,
  Gruppen-Mindestbestand) inkl. Einkaufsliste
- Einfache Gruppen-Auto-Zuordnung aus OFF-Kategorie im Produktformular
- Verlauf-Seite (Bewegungen: wer/was/wann) via neuem /movements-Endpoint
- Einstellungen-Seite (Ablauf-Warnfrist)
- Lagerorte mit optional uebergeordnetem Ort (verschachtelbar)

Backend:
- groups: PATCH + Anreicherung (product_count, stock)
- views: /shopping-list/groups, /movements
- schemas: GroupUpdate, GroupShoppingItem, MovementOut

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/routers/groups.py

@@ -3,17 +3,27 @@ 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
+from ..models import Group, Product, User
+from ..schemas import GroupCreate, GroupOut, GroupUpdate
+from ..services.stock import current_stock
 
 router = APIRouter(prefix="/groups", tags=["groups"])
 
 
+def _group_to_out(db: Session, group: Group) -> GroupOut:
+    out = GroupOut.model_validate(group)
+    products = db.query(Product).filter(Product.group_id == group.id).all()
+    out.product_count = len(products)
+    out.stock = float(sum(current_stock(db, p.id) for p in products))
+    return out
+
+
 @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()
+) -> list[GroupOut]:
+    groups = db.query(Group).order_by(Group.name).all()
+    return [_group_to_out(db, g) for g in groups]
 
 
 @router.post("", response_model=GroupOut, status_code=status.HTTP_201_CREATED)
@@ -21,14 +31,40 @@ def create_group(
     payload: GroupCreate,
     db: Session = Depends(get_db),
     _: User = Depends(require_admin),
-) -> Group:
+) -> GroupOut:
     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
+    return _group_to_out(db, group)
+
+
+@router.patch("/{group_id}", response_model=GroupOut)
+def update_group(
+    group_id: int,
+    payload: GroupUpdate,
+    db: Session = Depends(get_db),
+    _: User = Depends(require_admin),
+) -> GroupOut:
+    group = db.get(Group, group_id)
+    if group is None:
+        raise HTTPException(status.HTTP_404_NOT_FOUND, "Gruppe nicht gefunden")
+    data = payload.model_dump(exclude_unset=True)
+    if "name" in data and data["name"]:
+        clash = (
+            db.query(Group)
+            .filter(Group.name == data["name"], Group.id != group_id)
+            .first()
+        )
+        if clash:
+            raise HTTPException(status.HTTP_409_CONFLICT, "Name bereits vergeben")
+    for field, value in data.items():
+        setattr(group, field, value)
+    db.commit()
+    db.refresh(group)
+    return _group_to_out(db, group)
 
 
 @router.delete("/{group_id}", status_code=status.HTTP_204_NO_CONTENT)