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/core/router/app_router.dart

@@ -12,7 +12,9 @@ import '../../features/scan/scan_screen.dart';
 import '../../features/scan/recognition_confirm_screen.dart';
 import '../../features/scan/dish_result_screen.dart';
 import '../../features/scan/recognition_service.dart';
+import '../../features/menu/diary_screen.dart';
 import '../../features/menu/menu_screen.dart';
+import '../../features/menu/shopping_list_screen.dart';
 import '../../features/recipes/recipe_detail_screen.dart';
 import '../../features/recipes/recipes_screen.dart';
 import '../../features/profile/profile_screen.dart';
@@ -62,6 +64,22 @@ final routerProvider = Provider<GoRouter>((ref) {
         path: '/products/add',
         builder: (_, __) => const AddProductScreen(),
       ),
+      // Shopping list — full-screen, no bottom nav.
+      GoRoute(
+        path: '/menu/shopping-list',
+        builder: (context, state) {
+          final week = state.extra as String? ?? '';
+          return ShoppingListScreen(week: week);
+        },
+      ),
+      // Diary — full-screen, no bottom nav.
+      GoRoute(
+        path: '/menu/diary',
+        builder: (context, state) {
+          final date = state.extra as String? ?? '';
+          return DiaryScreen(date: date);
+        },
+      ),
       // Scan / recognition flow — all without bottom nav.
       GoRoute(
         path: '/scan',