Fix order saving, isMyOrder, blocked waiters, options pricing; add preferences, table groups, product images

Backend:
- OrderItemInput accepts option objects {id,name,price_delta} instead of int IDs
- extra_cost from selected options added to unit_price snapshot
- GET /api/products/?all=true for manager (includes unavailable)
- PUT /api/products/{id} now replaces options, ingredients, preference_sets
- POST /api/products/{id}/image — persistent image upload to /app/data/product_images
- New models: ProductPreferenceSet, ProductPreferenceChoice, TableGroup
- tables: group_id FK, hard delete (?hard=true), batch create POST /api/tables/batch
- GET /api/tables/groups + POST/PUT/DELETE groups endpoints
- POST /api/auth/me endpoint for token rehydration
- Auto-migration on startup for new columns

PWA:
- AuthRehydrator: fetches /auth/me on load so isMyOrder works after page reload
- 401 response force-logs out (covers blocked waiters)
- ItemOptionsModal: uses extra_cost correctly, shows preferences as radio buttons

Manager:
- ProductsPage: shows unavailable products greyed out, category color picker + reorder,
  full option/ingredient/preference editing, image upload
- TablesPage: table groups, auto-increment, deactivate vs hard delete, batch add

docker-compose.yml

@@ -10,6 +10,7 @@ services:
       - ./local_backend/pos.db:/app/pos.db
       - ./local_backend/license_state.json:/app/license_state.json
       - ./logo.png:/app/logo.png:ro
+      - ./data/product_images:/app/data/product_images
     extra_hosts:
       - "host.docker.internal:host-gateway"