feat(shopping): photo par article dans le catalogue

- Upload photo (context=product → thumbnail 150×150) dans CatalogueModal
- Miniature affichée dans la liste et dans le formulaire
- Schémas ProductCreate/Update/Response exposent image_path + thumbnail_path
- Backend sert /media/* via StaticFiles (FastAPI)
- Proxy /media → backend dans vite.config et nginx.conf

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/schemas/shopping.py

@@ -38,6 +38,8 @@ class ProductCreate(BaseModel):
     price: Decimal | None = None
     quantity_per_unit: Decimal | None = None
     default_store_id: uuid.UUID | None = None
+    image_path: str | None = None
+    thumbnail_path: str | None = None
 
 
 class ProductUpdate(BaseModel):
@@ -50,6 +52,8 @@ class ProductUpdate(BaseModel):
     price: Decimal | None = None
     quantity_per_unit: Decimal | None = None
     default_store_id: uuid.UUID | None = None
+    image_path: str | None = None
+    thumbnail_path: str | None = None
 
 
 class ProductResponse(BaseModel):
@@ -65,6 +69,8 @@ class ProductResponse(BaseModel):
     quantity_per_unit: Decimal | None
     default_store_id: uuid.UUID | None
     frequency_score: int
+    image_path: str | None
+    thumbnail_path: str | None
 
 
 class ListItemCreate(BaseModel):