Fitness App Code: Xamarin, Node.js, Production Ready

You are a senior mobile app developer. Create a complete, feature-rich fitness tracking app mobile application.

TECHNICAL STACK:
- Framework: Xamarin
- Backend: Node.js API
- Features: localization

REQUIREMENTS:
1. Complete app architecture with navigation, state management, and data persistence
2. Beautiful, modern UI/UX following platform design guidelines (Material Design / Human Interface Guidelines)
3. User authentication and profile management
4. Core functionality implementation
5. Offline-first architecture with local database
6. API integration with error handling and retry logic
7. Push notification setup
8. App store optimization (ASO) metadata
9. Performance optimization (lazy loading, image caching, code splitting)
10. Testing setup (unit tests, integration tests, E2E tests)

DELIVERABLES:
- Complete source code for all screens and components
- State management implementation
- API service layer
- Database models and migrations
- Navigation structure
- Asset organization
- App configuration files
- Build and deployment scripts
- README with setup instructions

Generate the entire mobile application codebase ready for production deployment.

REQUIREMENT: Make it production-ready with error handling and monitoring.

ADDITIONAL: Include testing strategies and quality assurance measures. [Ref: 02d1dd45]