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>

client/lib/shared/models/menu.dart

@@ -0,0 +1,151 @@
+import 'recipe.dart';
+
+class MenuPlan {
+  final String id;
+  final String weekStart;
+  final List<MenuDay> days;
+
+  const MenuPlan({
+    required this.id,
+    required this.weekStart,
+    required this.days,
+  });
+
+  factory MenuPlan.fromJson(Map<String, dynamic> json) {
+    return MenuPlan(
+      id: json['id'] as String? ?? '',
+      weekStart: json['week_start'] as String? ?? '',
+      days: (json['days'] as List<dynamic>? ?? [])
+          .map((e) => MenuDay.fromJson(e as Map<String, dynamic>))
+          .toList(),
+    );
+  }
+}
+
+class MenuDay {
+  final int day;
+  final String date;
+  final List<MealSlot> meals;
+  final double totalCalories;
+
+  const MenuDay({
+    required this.day,
+    required this.date,
+    required this.meals,
+    required this.totalCalories,
+  });
+
+  factory MenuDay.fromJson(Map<String, dynamic> json) {
+    return MenuDay(
+      day: json['day'] as int? ?? 0,
+      date: json['date'] as String? ?? '',
+      meals: (json['meals'] as List<dynamic>? ?? [])
+          .map((e) => MealSlot.fromJson(e as Map<String, dynamic>))
+          .toList(),
+      totalCalories: (json['total_calories'] as num?)?.toDouble() ?? 0,
+    );
+  }
+
+  // Localized day name.
+  String get dayName {
+    const names = [
+      'Понедельник',
+      'Вторник',
+      'Среда',
+      'Четверг',
+      'Пятница',
+      'Суббота',
+      'Воскресенье',
+    ];
+    final i = day - 1;
+    return (i >= 0 && i < names.length) ? names[i] : 'День $day';
+  }
+
+  // Short date label like "16 фев".
+  String get shortDate {
+    try {
+      final dt = DateTime.parse(date);
+      const months = [
+        'янв', 'фев', 'мар', 'апр', 'май', 'июн',
+        'июл', 'авг', 'сен', 'окт', 'ноя', 'дек',
+      ];
+      return '${dt.day} ${months[dt.month - 1]}';
+    } catch (_) {
+      return date;
+    }
+  }
+}
+
+class MealSlot {
+  final String id;
+  final String mealType;
+  final MenuRecipe? recipe;
+
+  const MealSlot({
+    required this.id,
+    required this.mealType,
+    this.recipe,
+  });
+
+  factory MealSlot.fromJson(Map<String, dynamic> json) {
+    return MealSlot(
+      id: json['id'] as String? ?? '',
+      mealType: json['meal_type'] as String? ?? '',
+      recipe: json['recipe'] != null
+          ? MenuRecipe.fromJson(json['recipe'] as Map<String, dynamic>)
+          : null,
+    );
+  }
+
+  String get mealLabel {
+    switch (mealType) {
+      case 'breakfast':
+        return 'Завтрак';
+      case 'lunch':
+        return 'Обед';
+      case 'dinner':
+        return 'Ужин';
+      default:
+        return mealType;
+    }
+  }
+
+  String get mealEmoji {
+    switch (mealType) {
+      case 'breakfast':
+        return '🌅';
+      case 'lunch':
+        return '☀️';
+      case 'dinner':
+        return '🌙';
+      default:
+        return '🍽️';
+    }
+  }
+}
+
+class MenuRecipe {
+  final String id;
+  final String title;
+  final String imageUrl;
+  final NutritionInfo? nutrition;
+
+  const MenuRecipe({
+    required this.id,
+    required this.title,
+    required this.imageUrl,
+    this.nutrition,
+  });
+
+  factory MenuRecipe.fromJson(Map<String, dynamic> json) {
+    return MenuRecipe(
+      id: json['id'] as String? ?? '',
+      title: json['title'] as String? ?? '',
+      imageUrl: json['image_url'] as String? ?? '',
+      nutrition: json['nutrition_per_serving'] != null
+          ? NutritionInfo.fromJson(
+              json['nutrition_per_serving'] as Map<String, dynamic>)
+          : null,
+    );
+  }
+}