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/internal/domain/diary/mocks/repository.go

@@ -6,6 +6,30 @@ import (
 	"github.com/food-ai/backend/internal/domain/diary"
 )
 
+// MockDishRepository is a test double implementing diary.DishRepository.
+type MockDishRepository struct {
+	FindOrCreateFn func(ctx context.Context, name string) (string, bool, error)
+}
+
+func (m *MockDishRepository) FindOrCreate(ctx context.Context, name string) (string, bool, error) {
+	if m.FindOrCreateFn != nil {
+		return m.FindOrCreateFn(ctx, name)
+	}
+	return "", false, nil
+}
+
+// MockRecipeRepository is a test double implementing diary.RecipeRepository.
+type MockRecipeRepository struct {
+	FindOrCreateRecipeFn func(ctx context.Context, dishID string, calories, proteinG, fatG, carbsG float64) (string, bool, error)
+}
+
+func (m *MockRecipeRepository) FindOrCreateRecipe(ctx context.Context, dishID string, calories, proteinG, fatG, carbsG float64) (string, bool, error) {
+	if m.FindOrCreateRecipeFn != nil {
+		return m.FindOrCreateRecipeFn(ctx, dishID, calories, proteinG, fatG, carbsG)
+	}
+	return "", false, nil
+}
+
 // MockDiaryRepository is a test double implementing diary.DiaryRepository.
 type MockDiaryRepository struct {
 	ListByDateFn func(ctx context.Context, userID, date string) ([]*diary.Entry, error)