add favorite

lib/features/favorites/domain/repositories/favorites_repository.dart

@@ -0,0 +1,29 @@
+import 'package:worker/features/products/domain/entities/product.dart';
+
+/// Favorites Repository Interface
+///
+/// Defines the contract for favorites data operations.
+/// Implementations should follow the online-first approach:
+/// 1. Try to fetch/update data from API
+/// 2. Update local cache with API response
+/// 3. On network failure, fall back to local cache
+abstract class FavoritesRepository {
+  /// Get favorite products with full product data
+  ///
+  /// Online-first: Fetches from wishlist API, caches locally.
+  /// Falls back to local cache on network failure.
+  /// Returns `List<Product>` with complete product information.
+  Future<List<Product>> getFavoriteProducts();
+
+  /// Add a product to favorites
+  ///
+  /// Online-first: Adds to API, then caches locally.
+  /// On network failure, queues for later sync.
+  Future<void> addFavorite(String productId);
+
+  /// Remove a product from favorites
+  ///
+  /// Online-first: Removes from API, then updates local cache.
+  /// On network failure, queues for later sync.
+  Future<bool> removeFavorite(String productId);
+}