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/mocks/repository.go

@@ -35,6 +35,7 @@ type MockDiaryRepository struct {
 	ListByDateFn func(ctx context.Context, userID, date string) ([]*diary.Entry, error)
 	CreateFn     func(ctx context.Context, userID string, req diary.CreateRequest) (*diary.Entry, error)
 	DeleteFn     func(ctx context.Context, id, userID string) error
+	GetRecentFn  func(ctx context.Context, userID string, limit int) ([]*diary.RecentDiaryItem, error)
 }
 
 func (m *MockDiaryRepository) ListByDate(ctx context.Context, userID, date string) ([]*diary.Entry, error) {
@@ -48,3 +49,10 @@ func (m *MockDiaryRepository) Create(ctx context.Context, userID string, req dia
 func (m *MockDiaryRepository) Delete(ctx context.Context, id, userID string) error {
 	return m.DeleteFn(ctx, id, userID)
 }
+
+func (m *MockDiaryRepository) GetRecent(ctx context.Context, userID string, limit int) ([]*diary.RecentDiaryItem, error) {
+	if m.GetRecentFn != nil {
+		return m.GetRecentFn(ctx, userID, limit)
+	}
+	return []*diary.RecentDiaryItem{}, nil
+}