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/features/scan/recognition_service.dart

@@ -22,7 +22,7 @@ class RecognizedItem {
   String unit;
   final String category;
   final double confidence;
-  final String? mappingId;
+  final String? primaryProductId;
   final int storageDays;
 
   RecognizedItem({
@@ -31,7 +31,7 @@ class RecognizedItem {
     required this.unit,
     required this.category,
     required this.confidence,
-    this.mappingId,
+    this.primaryProductId,
     required this.storageDays,
   });
 
@@ -42,7 +42,7 @@ class RecognizedItem {
       unit: json['unit'] as String? ?? 'pcs',
       category: json['category'] as String? ?? 'other',
       confidence: (json['confidence'] as num?)?.toDouble() ?? 0.0,
-      mappingId: json['mapping_id'] as String?,
+      primaryProductId: json['mapping_id'] as String?,
       storageDays: json['storage_days'] as int? ?? 7,
     );
   }