feat: slim meal_diary — derive name and nutrition from dish/recipe

Remove denormalized columns (name, calories, protein_g, fat_g, carbs_g)
from meal_diary. Name is now resolved via JOIN with dishes/dish_translations;
macros are computed as recipe.*_per_serving * portions at query time.

- Add dish.Repository.FindOrCreateRecipe: finds or creates a minimal recipe
  stub seeded with AI-estimated macros
- recognition/handler: resolve recipe_id synchronously per candidate;
  simplify enrichDishInBackground to translations-only
- diary/handler: accept dish_id OR name; always resolve recipe_id via
  FindOrCreateRecipe before INSERT
- diary/entity: DishID is now non-nullable string; CreateRequest drops macros
- diary/repository: ListByDate and Create use JOIN to return computed macros
- ai/types: add RecipeID field to DishCandidate
- Update tests and wire_gen accordingly

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

backend/cmd/server/wire_gen.go

@@ -54,11 +54,11 @@ func initRouter(appConfig *config.Config, pool *pgxpool.Pool) (http.Handler, err
 	ingredientRepository := ingredient.NewRepository(pool)
 	ingredientHandler := ingredient.NewHandler(ingredientRepository)
 	productHandler := product.NewHandler(productRepository)
-	recognitionHandler := recognition.NewHandler(client, ingredientRepository)
+	recognitionHandler := recognition.NewHandler(client, ingredientRepository, dishRepository)
 	menuRepository := menu.NewRepository(pool)
 	menuHandler := menu.NewHandler(menuRepository, client, pexelsClient, repository, productRepository, dishRepository)
 	diaryRepository := diary.NewRepository(pool)
-	diaryHandler := diary.NewHandler(diaryRepository)
+	diaryHandler := diary.NewHandler(diaryRepository, dishRepository, dishRepository)
 	homeHandler := home.NewHandler(pool)
 	dishHandler := dish.NewHandler(dishRepository)
 	recipeRepository := recipe.NewRepository(pool)