feat: rename ingredients→products, products→user_products; add barcode/OFF import

- Rename catalog: ingredient/* → product/* (canonical_name, barcode, nutrition per 100g)
- Rename pantry: product/* → userproduct/* (user-owned items with expiry)
- Squash migrations into single 001_initial_schema.sql (clean-db baseline)
- product_categories: add English canonical name column; fix COALESCE in queries
- Remove product_translations: product names are stored in their original language
- Add default_unit_name to product API responses via unit_translations JOIN
- Add cmd/importoff: bulk import from OpenFoodFacts JSONL dump (COPY + ON CONFLICT)
- Diary: support product_id entries alongside dish_id (CHECK num_nonnulls = 1)
- Home: getLoggedCalories joins both recipes and catalog products
- Flutter: rename models/providers/services to match backend rename
- Flutter: add barcode scan flow for diary (mobile_scanner, product_portion_sheet)
- Flutter: localise 6 new keys across 12 languages (barcode scan, portion weight)
- Routes: GET /products/search, GET /products/barcode/{barcode}, /user-products

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/lib/core/router/app_router.dart

@@ -21,7 +21,7 @@ import '../../features/menu/shopping_list_screen.dart';
 import '../../features/recipes/recipe_detail_screen.dart';
 import '../../features/recipes/recipes_screen.dart';
 import '../../features/profile/profile_screen.dart';
-import '../../features/products/product_provider.dart';
+import '../../features/products/user_product_provider.dart';
 import '../../features/scan/recognition_history_screen.dart';
 import '../../shared/models/recipe.dart';
 import '../../shared/models/saved_recipe.dart';
@@ -205,7 +205,7 @@ class MainShell extends ConsumerWidget {
     final currentIndex = _tabs.indexOf(location).clamp(0, _tabs.length - 1);
 
     // Count products expiring soon for the badge.
-    final expiringCount = ref.watch(productsProvider).maybeWhen(
+    final expiringCount = ref.watch(userProductsProvider).maybeWhen(
           data: (products) => products.where((p) => p.expiringSoon).length,
           orElse: () => 0,
         );