Modernize Objective-C App to Swift & SwiftUI

Your task is to help modernize an 11-year-old Objective-C app by converting it into a fully modern Swift and SwiftUI application. Follow these core requirements:

1. **Zero Data Loss**  
Ensure the existing database is preserved. The new Swift-based data layer must integrate seamlessly with current data, so users can update the app without losing any information.

2. **Responsive UI**  
Rebuild the entire UI using SwiftUI. It should be adaptive and responsive across all modern iPhone and iPad screen sizes and support features like dark mode and dynamic type.

3. **Eliminate Legacy Assets**  
Replace all legacy `.png` UI assets (such as icons, buttons, and color bars) with native SwiftUI components. Use SwiftUI Shapes, Colors, and SF Symbols for modern, scalable visuals.

4. **Full Swift Conversion**  
Remove all Objective-C view controllers. Use the SwiftUI app lifecycle as the main entry point and recreate all views and navigation—including the side menu—in pure SwiftUI.

Ensure the codebase is maintainable, performant, and aligned with Apple’s latest design and development standards.