feat: translate recommendations and menu dishes into user language

- Generate recipes in English (reverted prompt to English-only)
- Add TranslateRecipes to OpenAI client (translate.go) — sends compact
  JSON payload of translatable fields, merges back into original recipes
- recommendation/handler.go: translate recipes in-memory before response
  when lang != "en"; falls back to English on error
- dish/repository.go: Create() now returns (dishID, recipeID, err) so
  callers can upsert dish_translations after saving
- menu/handler.go: saveRecipes returns savedRecipeEntry slice with dishID;
  saveDishTranslations calls TranslateRecipes then UpsertTranslation for
  each dish when the request locale is not English
- savedrecipe/repository.go: updated to ignore dishID from Create()
- init.go: wire openaiClient as RecipeTranslator and dishRepository as
  DishTranslator for menu.NewHandler

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

backend/internal/domain/savedrecipe/repository.go

@@ -136,10 +136,10 @@ func (r *Repository) Save(ctx context.Context, userID string, req SaveRequest) (
 			}
 		}
 
-		var err error
-		recipeID, err = r.dishRepo.Create(ctx, cr)
-		if err != nil {
-			return nil, fmt.Errorf("create dish+recipe: %w", err)
+		var saveError error
+		_, recipeID, saveError = r.dishRepo.Create(ctx, cr)
+		if saveError != nil {
+			return nil, fmt.Errorf("create dish+recipe: %w", saveError)
 		}
 	}