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/screens/settings_screen.dart

@@ -1,24 +1,13 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/foundation.dart' show kIsWeb;
 import 'package:provider/provider.dart';
-import '../providers/app_lock_provider.dart';
 import '../providers/notification_provider.dart';
-import '../providers/subscription_provider.dart';
-import '../providers/navigation_provider.dart';
-import 'package:share_plus/share_plus.dart';
-import 'package:path_provider/path_provider.dart';
 import 'dart:io';
-import 'package:path/path.dart' as path;
 import '../services/notification_service.dart';
-import '../screens/sms_scan_screen.dart';
 import 'package:url_launcher/url_launcher.dart';
 import '../providers/theme_provider.dart';
 import '../theme/adaptive_theme.dart';
-import '../widgets/glassmorphic_scaffold.dart';
-import '../widgets/glassmorphic_app_bar.dart';
 import '../widgets/glassmorphism_card.dart';
-import '../widgets/app_navigator.dart';
-import '../theme/app_colors.dart';
 
 class SettingsScreen extends StatelessWidget {
   const SettingsScreen({super.key});
@@ -76,65 +65,7 @@ class SettingsScreen extends StatelessWidget {
     );
   }
 
-  Future<void> _backupData(BuildContext context) async {
-    try {
-      final provider = context.read<SubscriptionProvider>();
-      final subscriptions = provider.subscriptions;
 
-      // 임시 디렉토리에 백업 파일 생성
-      final tempDir = await getTemporaryDirectory();
-      final backupFile =
-          File(path.join(tempDir.path, 'submanager_backup.json'));
-
-      // 구독 데이터를 JSON 형식으로 저장
-      final jsonData = subscriptions
-          .map((sub) => {
-                'id': sub.id,
-                'serviceName': sub.serviceName,
-                'monthlyCost': sub.monthlyCost,
-                'billingCycle': sub.billingCycle,
-                'nextBillingDate': sub.nextBillingDate.toIso8601String(),
-                'isAutoDetected': sub.isAutoDetected,
-                'repeatCount': sub.repeatCount,
-                'lastPaymentDate': sub.lastPaymentDate?.toIso8601String(),
-              })
-          .toList();
-
-      await backupFile.writeAsString(jsonData.toString());
-
-      // 파일 공유
-      await Share.shareXFiles(
-        [XFile(backupFile.path)],
-        text: 'SubManager 백업 파일',
-      );
-
-      if (context.mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          const SnackBar(content: Text('백업 파일이 생성되었습니다')),
-        );
-      }
-    } catch (e) {
-      if (context.mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text('백업 중 오류가 발생했습니다: $e')),
-        );
-      }
-    }
-  }
-
-  // SMS 스캔 화면으로 이동
-  void _navigateToSmsScan(BuildContext context) async {
-    final added = await Navigator.push<bool>(
-      context,
-      MaterialPageRoute(builder: (context) => const SmsScanScreen()),
-    );
-
-    if (added == true && context.mounted) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        const SnackBar(content: Text('구독이 성공적으로 추가되었습니다')),
-      );
-    }
-  }
 
   @override
   Widget build(BuildContext context) {
@@ -455,10 +386,10 @@ class SettingsScreen extends StatelessWidget {
           ),
 
           // 데이터 관리
-          GlassmorphismCard(
+          const GlassmorphismCard(
             margin: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
             padding: const EdgeInsets.all(8),
-            child: Column(
+            child: const Column(
               children: [
                 // 데이터 백업 기능 비활성화
                 // ListTile(