feat: food search sheet with FTS+trgm, dish/recent endpoints, multilingual aliases

Backend:
- GET /dishes/search — hybrid FTS (english + simple) + trgm + ILIKE search
- GET /diary/recent — recently used dishes and products for the current user
- product search upgraded: FTS on canonical_name and product_aliases, ranked by GREATEST(ts_rank, similarity)
- importoff: collect product_name_ru/de/fr/... as product_aliases for multilingual search (e.g. "сникерс" → "Snickers")
- migrations: FTS + trgm indexes merged into 001_initial_schema.sql (002 removed)

Flutter:
- FoodSearchSheet: debounced search field, recently-used section, product/dish results, scan-photo and barcode chips
- DishPortionSheet: quick ½/1/1½/2 buttons + custom input
- + button in meal card now opens FoodSearchSheet instead of going directly to AI scan
- 7 new l10n keys across all 12 languages

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

backend/internal/domain/diary/entity.go

@@ -22,6 +22,18 @@ type Entry struct {
 	CreatedAt time.Time `json:"created_at"`
 }
 
+// RecentDiaryItem is a lightweight summary of a recently logged product or dish.
+type RecentDiaryItem struct {
+	ItemType           string   `json:"item_type"` // "dish" | "product"
+	DishID             *string  `json:"dish_id,omitempty"`
+	ProductID          *string  `json:"product_id,omitempty"`
+	Name               string   `json:"name"`
+	ImageURL           *string  `json:"image_url,omitempty"`
+	CategoryName       *string  `json:"category_name,omitempty"`
+	CaloriesPer100g    *float64 `json:"calories_per_100g,omitempty"`
+	CaloriesPerServing *float64 `json:"calories_per_serving,omitempty"`
+}
+
 // CreateRequest is the body for POST /diary.
 type CreateRequest struct {
 	Date      string   `json:"date"`