fix: align frontend API calls with backend routes and types

- Backend: rename routes /mealplan→/mealplans, /shoppinglist→/shopping
- Backend: simplify swap/reroll to entry-centric endpoints (by entryId)
- Frontend: fix all interfaces to use string GUIDs instead of numbers
- Frontend: fix field names (weekStart, date, totalAmount) to match backend JSON
- Frontend: shopping toggle by itemName instead of non-existent id
- Frontend: handle 204 No Content on DELETE responses
- Docker-compose: use env vars for DB credentials

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/Controllers/ShoppingListController.cs

@@ -5,7 +5,7 @@ using MealPlanner.Services;
 namespace MealPlanner.Controllers;
 
 [ApiController]
-[Route("api/shoppinglist")]
+[Route("api/shopping")]
 [Authorize]
 public class ShoppingListController(ShoppingListService shoppingListService) : ControllerBase
 {