Refactor screens to MVC architecture with modular widgets

- Extract business logic from screens into dedicated controllers
- Split large screen files into smaller, reusable widget components
- Add controllers for AddSubscriptionScreen and DetailScreen
- Create modular widgets for subscription and detail features
- Improve code organization and maintainability
- Remove duplicated code and improve reusability

🤖 Generated with [Claude Code](https://claude.ai/code)

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

lib/widgets/app_navigator.dart

@@ -1,12 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:provider/provider.dart';
-import '../screens/main_screen.dart';
-import '../screens/analysis_screen.dart';
-import '../screens/add_subscription_screen.dart';
-import '../screens/detail_screen.dart';
-import '../screens/settings_screen.dart';
-import '../screens/sms_scan_screen.dart';
 import '../screens/category_management_screen.dart';
 import '../screens/app_lock_screen.dart';
 import '../models/subscription_model.dart';