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.g.dart

@@ -10,7 +10,7 @@ IngredientMapping _$IngredientMappingFromJson(Map<String, dynamic> json) =>
     IngredientMapping(
       id: json['id'] as String,
       canonicalName: json['canonical_name'] as String,
-      canonicalNameRu: json['canonical_name_ru'] as String?,
+      categoryName: json['category_name'] as String?,
       category: json['category'] as String?,
       defaultUnit: json['default_unit'] as String?,
       storageDays: (json['storage_days'] as num?)?.toInt(),
@@ -20,7 +20,7 @@ Map<String, dynamic> _$IngredientMappingToJson(IngredientMapping instance) =>
     <String, dynamic>{
       'id': instance.id,
       'canonical_name': instance.canonicalName,
-      'canonical_name_ru': instance.canonicalNameRu,
+      'category_name': instance.categoryName,
       'category': instance.category,
       'default_unit': instance.defaultUnit,
       'storage_days': instance.storageDays,