Implement new UI design system

Implement the new design system for iOS app v3.0.

Design System Components:

• Typography (SF Pro, dynamic type support)
• Color palette (light/dark mode)
• Spacing system
• Component library (buttons, cards, lists, forms)
• Icons and imagery
• Animations and transitions

Implementation:

• Create SwiftUI component library
• Implement theme system
• Add dark mode support
• Create Xcode previews for all components
• Document component usage
• Add accessibility labels
• Test with VoiceOver

Dependencies: Relates to Android app UI design (need consistency)