feat: add rematch functionality for recipe ingredients and enhance inventory management

- Added a new API path for rematching recipe ingredients in `api_paths.dart`.
- Implemented a manual product creation dialog in `inventory_screen.dart` to allow users to create new products directly.
- Integrated the rematch functionality in `recipe_repository.dart` to handle rematching of recipe ingredients.
- Updated the recipe detail screen to include a button for triggering the rematch process.
- Introduced a new `RecipeMatchingService` in the backend to handle ingredient matching logic.
- Added database migration to include `aiEngineEnabled` column in the User table.

Co-authored-by: Copilot <copilot@github.com>

flutter/lib/core/api/api_paths.dart

@@ -46,6 +46,7 @@ class RecipeApiPaths {
   static String unshare(int id, String username) => '/recipes/$id/share/${Uri.encodeComponent(username)}';
   static String inventoryPreview(int id) => '/recipes/$id/inventory-preview';
   static String analysis(int id) => '/recipes/$id/analysis';
+  static String rematch(int id) => '/recipes/$id/rematch';
   static const parseMarkdown = '/recipes/parse-markdown';
   static const aiSuggestions = '/recipes/ai-suggestions';
 }