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>

backend/internal/gemini/recognition.go

@@ -40,18 +40,25 @@ type DishResult struct {
 	SimilarDishes []string `json:"similar_dishes"`
 }
 
+// IngredientTranslation holds the localized name and aliases for one language.
+type IngredientTranslation struct {
+	Lang    string   `json:"lang"`
+	Name    string   `json:"name"`
+	Aliases []string `json:"aliases"`
+}
+
 // IngredientClassification is the AI-produced classification of an unknown food item.
 type IngredientClassification struct {
-	CanonicalName   string   `json:"canonical_name"`
-	CanonicalNameRu string   `json:"canonical_name_ru"`
-	Category        string   `json:"category"`
-	DefaultUnit     string   `json:"default_unit"`
-	CaloriesPer100g *float64 `json:"calories_per_100g"`
-	ProteinPer100g  *float64 `json:"protein_per_100g"`
-	FatPer100g      *float64 `json:"fat_per_100g"`
-	CarbsPer100g    *float64 `json:"carbs_per_100g"`
-	StorageDays     int      `json:"storage_days"`
-	Aliases         []string `json:"aliases"`
+	CanonicalName   string                  `json:"canonical_name"`
+	Aliases         []string                `json:"aliases"`      // English aliases
+	Translations    []IngredientTranslation `json:"translations"` // other languages
+	Category        string                  `json:"category"`
+	DefaultUnit     string                  `json:"default_unit"`
+	CaloriesPer100g *float64                `json:"calories_per_100g"`
+	ProteinPer100g  *float64                `json:"protein_per_100g"`
+	FatPer100g      *float64                `json:"fat_per_100g"`
+	CarbsPer100g    *float64                `json:"carbs_per_100g"`
+	StorageDays     int                     `json:"storage_days"`
 }
 
 // RecognizeReceipt uses the vision model to extract food items from a receipt photo.
@@ -177,20 +184,21 @@ func (c *Client) RecognizeDish(ctx context.Context, imageBase64, mimeType string
 // ClassifyIngredient uses the text model to classify an unknown food item
 // and build an ingredient_mappings record for it.
 func (c *Client) ClassifyIngredient(ctx context.Context, name string) (*IngredientClassification, error) {
-	prompt := fmt.Sprintf(`Классифицируй продукт питания: "%s".
-
-Ответь ТОЛЬКО валидным JSON без markdown:
+	prompt := fmt.Sprintf(`Classify the food product: "%s".
+Return ONLY valid JSON without markdown:
 {
   "canonical_name": "turkey_breast",
-  "canonical_name_ru": "грудка индейки",
+  "aliases": ["turkey breast"],
+  "translations": [
+    {"lang": "ru", "name": "грудка индейки", "aliases": ["грудка индейки", "филе индейки"]}
+  ],
   "category": "meat",
   "default_unit": "g",
   "calories_per_100g": 135,
   "protein_per_100g": 29,
   "fat_per_100g": 1,
   "carbs_per_100g": 0,
-  "storage_days": 3,
-  "aliases": ["грудка индейки", "филе индейки", "turkey breast"]
+  "storage_days": 3
 }`, name)
 
 	messages := []map[string]string{