refactor: migrate ingredient aliases/categories to dedicated tables, drop spoonacular_id

- migration 012: create ingredient_categories + ingredient_category_translations
  tables (7 slugs, Russian names); add ingredient_aliases (ingredient_id, lang,
  alias) with GIN trigram index; migrate aliases JSONB from ingredient_mappings
  and ingredient_translations; drop aliases columns and spoonacular_id; add
  UNIQUE (canonical_name) as conflict key
- ingredient/model: remove SpoonacularID, add CategoryName for localized display
- ingredient/repository: conflict on canonical_name; GetByID/Search join category
  translations and aliases lateral; new UpsertAliases (pgx batch),
  UpsertCategoryTranslation; remove GetBySpoonacularID; split scan helpers into
  scanMappingWrite / scanMappingRead
- gemini/recognition: add IngredientTranslation type; IngredientClassification
  now carries Translations []IngredientTranslation instead of CanonicalNameRu;
  update ClassifyIngredient prompt to English with structured translations array
- recognition/handler: update ingredientRepo interface; saveClassification uses
  UpsertAliases and iterates Translations
- recipe/model: remove SpoonacularID from RecipeIngredient
- integration tests: remove SpoonacularID fixtures, replace GetBySpoonacularID
  tests with GetByID, add UpsertAliases and UpsertCategoryTranslation tests
- Flutter: remove canonicalNameRu from IngredientMapping, add categoryName;
  displayName returns server-resolved canonicalName; regenerate .g.dart

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

client/lib/shared/models/ingredient_mapping.dart

@@ -7,8 +7,8 @@ class IngredientMapping {
   final String id;
   @JsonKey(name: 'canonical_name')
   final String canonicalName;
-  @JsonKey(name: 'canonical_name_ru')
-  final String? canonicalNameRu;
+  @JsonKey(name: 'category_name')
+  final String? categoryName;
   final String? category;
   @JsonKey(name: 'default_unit')
   final String? defaultUnit;
@@ -18,14 +18,14 @@ class IngredientMapping {
   const IngredientMapping({
     required this.id,
     required this.canonicalName,
-    this.canonicalNameRu,
+    this.categoryName,
     this.category,
     this.defaultUnit,
     this.storageDays,
   });
 
-  /// Display name prefers Russian, falls back to canonical English name.
-  String get displayName => canonicalNameRu ?? canonicalName;
+  /// Display name is the server-resolved canonical name (language-aware from backend).
+  String get displayName => canonicalName;
 
   factory IngredientMapping.fromJson(Map<String, dynamic> json) =>
       _$IngredientMappingFromJson(json);