Backend: Mindestbestand je Lagerort für Produkte und Gruppen

Zusaetzlich zum globalen Mindestbestand: je Produkt und je Gruppe laesst sich pro
Lagerort ein Mindestbestand (in Artikeleinheiten) hinterlegen.
- Neue Tabellen product_location_min_stock / group_location_min_stock.
- PUT /products/{id}/location-min-stock und /groups/{id}/location-min-stock
  ersetzen die Eintraege; Produkt-/Gruppen-Ausgabe liefert sie mit.
- Neue Einkaufsliste GET /shopping-list/by-location: Bedarfe je Ort (Produkte +
  Gruppen), Bestand-am-Ort gegen Mindestbestand-am-Ort.
- Helfer location_stock_base (Bestand je Ort). 4 neue Tests, Suite 144 gruen.

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

backend/app/routers/views.py

@@ -1,3 +1,4 @@
+from collections import defaultdict
 from datetime import date, timedelta
 
 from fastapi import APIRouter, Depends
@@ -5,10 +6,27 @@ from sqlalchemy.orm import Session
 
 from ..database import get_db
 from ..deps import get_current_user
-from ..models import Group, Lot, Movement, Product, User
-from ..schemas import ExpiringItem, GroupShoppingItem, MovementOut, ShoppingItem
-from ..services.conversion import BASE_OF_KIND, display_unit_info
-from ..services.stock import current_stock
+from ..models import (
+    Group,
+    GroupLocationMinStock,
+    Location,
+    Lot,
+    Movement,
+    Product,
+    ProductLocationMinStock,
+    User,
+)
+from ..schemas import (
+    ExpiringItem,
+    GroupShoppingItem,
+    LocationNeedGroup,
+    LocationNeedProduct,
+    LocationNeeds,
+    MovementOut,
+    ShoppingItem,
+)
+from ..services.conversion import BASE_OF_KIND, article_unit, display_unit_info
+from ..services.stock import current_stock, location_stock_base
 from .settings import get_expiry_warning_days
 
 router = APIRouter(tags=["views"])
@@ -83,6 +101,64 @@ def group_shopping_list(
     return items
 
 
+@router.get("/shopping-list/by-location", response_model=list[LocationNeeds])
+def shopping_list_by_location(
+    db: Session = Depends(get_db), _: User = Depends(get_current_user)
+) -> list[LocationNeeds]:
+    """Bedarfe je Lagerort: Produkte und Gruppen, deren Bestand AN DIESEM ORT
+    unter dem dort hinterlegten Mindestbestand liegt."""
+    prod_needs: dict[int, list[LocationNeedProduct]] = defaultdict(list)
+    group_needs: dict[int, list[LocationNeedGroup]] = defaultdict(list)
+
+    for e in db.query(ProductLocationMinStock).all():
+        product = db.get(Product, e.product_id)
+        if product is None:
+            continue
+        faktor, label = article_unit(product)
+        stock = location_stock_base(db, product, e.location_id) / (faktor or 1.0)
+        if stock < e.min_stock:
+            prod_needs[e.location_id].append(LocationNeedProduct(
+                product_id=product.id, name=product.name, unit_label=label,
+                stock=round(stock, 3), min_stock=e.min_stock,
+                deficit=round(e.min_stock - stock, 3),
+            ))
+
+    for e in db.query(GroupLocationMinStock).all():
+        group = db.get(Group, e.group_id)
+        if group is None:
+            continue
+        unit = group.min_stock_unit
+        if unit is not None:
+            base = BASE_OF_KIND[unit.kind]
+            matching = [p for p in group.products if p.base_unit == base]
+            stock = sum(location_stock_base(db, p, e.location_id) for p in matching) / unit.factor
+            unit_name = unit.name
+        else:
+            stock = float(sum(location_stock_base(db, p, e.location_id) for p in group.products))
+            unit_name = ""
+        if stock < e.min_stock:
+            group_needs[e.location_id].append(LocationNeedGroup(
+                group_id=group.id, name=group.name, unit_name=unit_name,
+                stock=round(stock, 3), min_stock=e.min_stock,
+                deficit=round(e.min_stock - stock, 3),
+            ))
+
+    loc_ids = set(prod_needs) | set(group_needs)
+    namen = {
+        loc.id: loc.name
+        for loc in db.query(Location).filter(Location.id.in_(loc_ids)).all()
+    }
+    result: list[LocationNeeds] = []
+    for loc_id in sorted(loc_ids, key=lambda i: namen.get(i, "")):
+        result.append(LocationNeeds(
+            location_id=loc_id,
+            location_name=namen.get(loc_id, "?"),
+            products=sorted(prod_needs.get(loc_id, []), key=lambda x: x.deficit, reverse=True),
+            groups=sorted(group_needs.get(loc_id, []), key=lambda x: x.deficit, reverse=True),
+        ))
+    return result
+
+
 @router.get("/expiring", response_model=list[ExpiringItem])
 def expiring(
     days: int | None = None,