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/themed_text.dart

@@ -43,7 +43,6 @@ class ThemedText extends StatelessWidget {
     if (forceDark) return AppColors.textPrimary;
     
     final brightness = Theme.of(context).brightness;
-    final backgroundColor = Theme.of(context).scaffoldBackgroundColor;
     
     // 글래스모피즘 환경에서는 보통 어두운 배경 위에 밝은 텍스트
     if (_isGlassmorphicContext(context)) {