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/main.py

@@ -1,6 +1,7 @@
 from contextlib import asynccontextmanager
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
+from fastapi.staticfiles import StaticFiles
 from app.api.health import router as health_router
 from app.api.media import router as media_router
 from app.api.todos import router as todos_router
@@ -29,3 +30,5 @@ app.include_router(health_router, prefix="/api")
 app.include_router(media_router, prefix="/api/media")
 app.include_router(todos_router, prefix="/api/todos")
 app.include_router(shopping_router, prefix="/api/shopping")
+
+app.mount("/media", StaticFiles(directory=str(settings.upload_path)), name="media")