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/services/notification_service.dart

@@ -152,13 +152,6 @@ class NotificationService {
     }
   }
 
-  // 알림 서비스가 초기화되었는지 확인하는 메서드
-  static bool _isInitialized() {
-    // 웹 플랫폼인 경우 항상 false 반환
-    if (_isWeb) return false;
-    // 초기화 플래그 확인
-    return _initialized;
-  }
 
   static Future<bool> requestPermission() async {
     final result = await _notifications
@@ -182,7 +175,7 @@ class NotificationService {
     }
     
     try {
-      final androidDetails = AndroidNotificationDetails(
+      const androidDetails = AndroidNotificationDetails(
         'subscription_channel',
         '구독 알림',
         channelDescription: '구독 관련 알림을 보여줍니다.',
@@ -257,7 +250,7 @@ class NotificationService {
     try {
       final notificationId = subscription.id.hashCode;
 
-      final androidDetails = AndroidNotificationDetails(
+      const androidDetails = AndroidNotificationDetails(
         'subscription_channel',
         '구독 알림',
         channelDescription: '구독 만료 알림을 보내는 채널입니다.',
@@ -265,13 +258,13 @@ class NotificationService {
         priority: Priority.high,
       );
 
-      final iosDetails = DarwinNotificationDetails(
+      const iosDetails = DarwinNotificationDetails(
         presentAlert: true,
         presentBadge: true,
         presentSound: true,
       );
 
-      final notificationDetails = NotificationDetails(
+      const notificationDetails = NotificationDetails(
         android: androidDetails,
         iOS: iosDetails,
       );