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/main_screen.dart

@@ -1,7 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:provider/provider.dart';
-import '../providers/subscription_provider.dart';
 import '../providers/app_lock_provider.dart';
 import '../providers/navigation_provider.dart';
 import '../theme/app_colors.dart';
@@ -13,7 +12,6 @@ import 'sms_scan_screen.dart';
 import '../utils/animation_controller_helper.dart';
 import '../widgets/floating_navigation_bar.dart';
 import '../widgets/glassmorphic_scaffold.dart';
-import '../widgets/glassmorphic_app_bar.dart';
 import '../widgets/home_content.dart';
 
 class MainScreen extends StatefulWidget {
@@ -33,7 +31,6 @@ class _MainScreenState extends State<MainScreen>
   late AnimationController _waveController;
   late ScrollController _scrollController;
   late FloatingNavBarScrollController _navBarScrollController;
-  bool _isNavBarVisible = true;
   
   // 화면 목록
   late final List<Widget> _screens;
@@ -67,8 +64,8 @@ class _MainScreenState extends State<MainScreen>
     
     _navBarScrollController = FloatingNavBarScrollController(
       scrollController: _scrollController,
-      onHide: () => setState(() => _isNavBarVisible = false),
-      onShow: () => setState(() => _isNavBarVisible = true),
+      onHide: () {},
+      onShow: () {},
     );
 
     // 화면 목록 초기화
@@ -162,17 +159,18 @@ class _MainScreenState extends State<MainScreen>
       // 구독이 성공적으로 추가된 경우
       if (result == true) {
         // 상단에 스낵바 표시
+        if (!context.mounted) return;
         ScaffoldMessenger.of(context).showSnackBar(
           SnackBar(
-            content: Row(
+            content: const Row(
               children: [
-                const Icon(
+                Icon(
                   Icons.check_circle,
                   color: Colors.white,
                   size: 20,
                 ),
-                const SizedBox(width: 12),
-                const Text(
+                SizedBox(width: 12),
+                Text(
                   '구독이 추가되었습니다',
                   style: TextStyle(
                     fontSize: 16,