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/adapters/ai/types.go

@@ -96,6 +96,8 @@ type ReceiptResult struct {
 
 // DishCandidate is a single dish recognition candidate with estimated nutrition.
 type DishCandidate struct {
+	DishID      *string `json:"dish_id,omitempty"`
+	RecipeID    *string `json:"recipe_id,omitempty"`
 	DishName    string  `json:"dish_name"`
 	WeightGrams int     `json:"weight_grams"`
 	Calories    float64 `json:"calories"`

backend/internal/adapters/openai/dish.go

@@ -0,0 +1,97 @@
+package openai
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	"github.com/food-ai/backend/internal/adapters/ai"
+	"github.com/food-ai/backend/internal/infra/locale"
+)
+
+// GenerateRecipeForDish generates a single English recipe for a named dish.
+func (c *Client) GenerateRecipeForDish(ctx context.Context, dishName string) (*ai.Recipe, error) {
+	prompt := fmt.Sprintf(`You are a chef and nutritionist.
+Generate exactly 1 recipe for the dish "%s" in English.
+
+Requirements:
+- Include accurate macros per serving
+- Total cooking time: max 60 minutes
+
+IMPORTANT:
+- All text fields MUST be in English.
+- The "image_query" field MUST be in English.
+
+Return ONLY a valid JSON array with exactly one element, no markdown:
+[{"title":"...","description":"...","cuisine":"russian|asian|european|mediterranean|american|other","difficulty":"easy|medium|hard","prep_time_min":10,"cook_time_min":20,"servings":2,"image_query":"...","ingredients":[{"name":"...","amount":100,"unit":"..."}],"steps":[{"number":1,"description":"...","timer_seconds":null}],"tags":["..."],"nutrition_per_serving":{"calories":400,"protein_g":30,"fat_g":10,"carbs_g":40}}]`,
+		dishName)
+
+	var lastError error
+	for attempt := range maxRetries {
+		messages := []map[string]string{{"role": "user", "content": prompt}}
+		if attempt > 0 {
+			messages = append(messages, map[string]string{
+				"role":    "user",
+				"content": "Previous response was not valid JSON. Return ONLY a JSON array with no text before or after.",
+			})
+		}
+		text, generateError := c.generateContent(ctx, messages)
+		if generateError != nil {
+			return nil, generateError
+		}
+		recipes, parseError := parseRecipesJSON(text)
+		if parseError != nil {
+			lastError = parseError
+			continue
+		}
+		if len(recipes) == 0 {
+			lastError = fmt.Errorf("empty recipes array")
+			continue
+		}
+		recipes[0].Nutrition.Approximate = true
+		return &recipes[0], nil
+	}
+	return nil, fmt.Errorf("generate recipe for dish %q after %d attempts: %w", dishName, maxRetries, lastError)
+}
+
+// TranslateDishName translates a dish name into all supported languages (except English)
+// in a single AI call. Returns a map of lang-code → translated name.
+func (c *Client) TranslateDishName(ctx context.Context, name string) (map[string]string, error) {
+	var langLines []string
+	for _, language := range locale.Languages {
+		if language.Code != "en" {
+			langLines = append(langLines, fmt.Sprintf(`"%s": "%s"`, language.Code, language.EnglishName))
+		}
+	}
+	if len(langLines) == 0 {
+		return map[string]string{}, nil
+	}
+
+	prompt := fmt.Sprintf(`Translate the dish name "%s" into the following languages.
+Return ONLY a valid JSON object mapping language code to translated name, no markdown:
+{%s}
+Fill each value with the natural translation of the dish name in that language.`,
+		name, strings.Join(langLines, ", "))
+
+	text, generateError := c.generateContent(ctx, []map[string]string{
+		{"role": "user", "content": prompt},
+	})
+	if generateError != nil {
+		return nil, generateError
+	}
+
+	text = strings.TrimSpace(text)
+	if strings.HasPrefix(text, "```") {
+		text = strings.TrimPrefix(text, "```json")
+		text = strings.TrimPrefix(text, "```")
+		text = strings.TrimSuffix(text, "```")
+		text = strings.TrimSpace(text)
+	}
+
+	var translations map[string]string
+	if parseError := json.Unmarshal([]byte(text), &translations); parseError != nil {
+		return nil, fmt.Errorf("parse translations for %q: %w", name, parseError)
+	}
+	return translations, nil
+}