feat: implement Iteration 4 — menu planning, shopping list, diary

Backend:
- Migrations 007 (menu_plans, menu_items, shopping_lists) and
  008 (meal_diary)
- gemini/menu.go: GenerateMenu — 7-day × 3-meal plan via one Groq call
- internal/menu: model, repository (GetByWeek, SaveMenuInTx,
  shopping list CRUD), handler (GET/PUT/DELETE /menu,
  POST /ai/generate-menu, shopping list endpoints)
- internal/diary: model, repository, handler (GET/POST/DELETE /diary)
- Increase server WriteTimeout to 120s for long AI calls
- api_client.go: add patch() and postList() helpers

Flutter:
- shared/models: menu.dart, shopping_item.dart, diary_entry.dart
- features/menu: menu_service.dart, menu_provider.dart
  (MenuNotifier, ShoppingListNotifier, DiaryNotifier with family)
- MenuScreen: 7-day view, week nav, skeleton on generation,
  generate FAB with confirmation dialog
- ShoppingListScreen: items by category, optimistic checkbox toggle
- DiaryScreen: daily entries with swipe-to-delete, add-entry sheet
- Router: /menu/shopping-list and /menu/diary routes

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

backend/internal/gemini/menu.go

@@ -0,0 +1,168 @@
+package gemini
+
+import (
+	"context"
+	"fmt"
+	"strings"
+)
+
+// MenuRequest contains parameters for weekly menu generation.
+type MenuRequest struct {
+	UserGoal          string
+	DailyCalories     int
+	Restrictions      []string
+	CuisinePrefs      []string
+	AvailableProducts []string
+}
+
+// DayPlan is the AI-generated plan for a single day.
+type DayPlan struct {
+	Day   int         `json:"day"`
+	Meals []MealEntry `json:"meals"`
+}
+
+// MealEntry is a single meal within a day plan.
+type MealEntry struct {
+	MealType string `json:"meal_type"` // breakfast | lunch | dinner
+	Recipe   Recipe `json:"recipe"`
+}
+
+// GenerateMenu asks the model to plan 7 days × 3 meals.
+// Returns exactly 7 DayPlan items on success.
+func (c *Client) GenerateMenu(ctx context.Context, req MenuRequest) ([]DayPlan, error) {
+	prompt := buildMenuPrompt(req)
+	messages := []map[string]string{
+		{"role": "user", "content": prompt},
+	}
+
+	var lastErr error
+	for attempt := 0; attempt < maxRetries; attempt++ {
+		if attempt > 0 {
+			messages = append(messages, map[string]string{
+				"role":    "user",
+				"content": "Предыдущий ответ не был валидным JSON. Верни ТОЛЬКО объект JSON без какого-либо текста до или после.",
+			})
+		}
+
+		text, err := c.generateContent(ctx, messages)
+		if err != nil {
+			return nil, err
+		}
+
+		days, err := parseMenuJSON(text)
+		if err != nil {
+			lastErr = fmt.Errorf("attempt %d parse JSON: %w", attempt+1, err)
+			continue
+		}
+
+		for i := range days {
+			for j := range days[i].Meals {
+				days[i].Meals[j].Recipe.Nutrition.Approximate = true
+			}
+		}
+		return days, nil
+	}
+
+	return nil, fmt.Errorf("failed to parse valid JSON after %d attempts: %w", maxRetries, lastErr)
+}
+
+func buildMenuPrompt(req MenuRequest) string {
+	goalRu := map[string]string{
+		"weight_loss": "похудение",
+		"maintain":    "поддержание веса",
+		"gain":        "набор массы",
+	}
+	goal := goalRu[req.UserGoal]
+	if goal == "" {
+		goal = "поддержание веса"
+	}
+
+	restrictions := "нет"
+	if len(req.Restrictions) > 0 {
+		restrictions = strings.Join(req.Restrictions, ", ")
+	}
+
+	cuisines := "любые"
+	if len(req.CuisinePrefs) > 0 {
+		cuisines = strings.Join(req.CuisinePrefs, ", ")
+	}
+
+	calories := req.DailyCalories
+	if calories <= 0 {
+		calories = 2000
+	}
+
+	productsSection := ""
+	if len(req.AvailableProducts) > 0 {
+		productsSection = "\nПродукты в наличии (приоритет — скоро истекают ⚠):\n" +
+			strings.Join(req.AvailableProducts, "\n") +
+			"\nПо возможности используй эти продукты.\n"
+	}
+
+	return fmt.Sprintf(`Ты — диетолог-повар. Составь меню на 7 дней на русском языке.
+
+Профиль пользователя:
+- Цель: %s
+- Дневная норма калорий: %d ккал (завтрак 25%%, обед 40%%, ужин 35%%)
+- Ограничения: %s
+- Предпочтения кухни: %s
+%s
+Требования:
+- 3 приёма пищи в день: breakfast, lunch, dinner
+- Не повторять рецепты
+- КБЖУ на 1 порцию (приблизительно)
+- Поле image_query — ТОЛЬКО на английском языке (для поиска фото)
+
+Верни ТОЛЬКО валидный JSON без markdown:
+{
+  "days": [
+    {
+      "day": 1,
+      "meals": [
+        {
+          "meal_type": "breakfast",
+          "recipe": {
+            "title": "Название",
+            "description": "2-3 предложения",
+            "cuisine": "russian|asian|european|mediterranean|american|other",
+            "difficulty": "easy|medium|hard",
+            "prep_time_min": 5,
+            "cook_time_min": 10,
+            "servings": 1,
+            "image_query": "oatmeal apple breakfast bowl",
+            "ingredients": [{"name": "Овсянка", "amount": 80, "unit": "г"}],
+            "steps": [{"number": 1, "description": "...", "timer_seconds": null}],
+            "tags": ["быстрый завтрак"],
+            "nutrition_per_serving": {
+              "calories": 320, "protein_g": 8, "fat_g": 6, "carbs_g": 58
+            }
+          }
+        },
+        {"meal_type": "lunch", "recipe": {...}},
+        {"meal_type": "dinner", "recipe": {...}}
+      ]
+    }
+  ]
+}`, goal, calories, restrictions, cuisines, productsSection)
+}
+
+func parseMenuJSON(text string) ([]DayPlan, error) {
+	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 wrapper struct {
+		Days []DayPlan `json:"days"`
+	}
+	if err := parseJSON(text, &wrapper); err != nil {
+		return nil, err
+	}
+	if len(wrapper.Days) == 0 {
+		return nil, fmt.Errorf("empty days array in response")
+	}
+	return wrapper.Days, nil
+}