Add new platform service methods for direct file saving alongside existing share functionality:
- Add saveToDevice() and saveAs() methods to PlatformService interface
- Implement cross-platform support in WebPlatformService, ElectronPlatformService, and CapacitorPlatformService
- Update DataExportSection UI to provide Share Contacts and Save to Device buttons
- Add AndroidFileSaver plugin architecture with fallback implementation
- Include comprehensive documentation for native Android plugin implementation
This addresses the Android simulator file sharing limitation by providing users with clear choices between app-to-app sharing and direct device storage, while maintaining backward compatibility across all platforms.
- CapacitorPlatformService: Add MediaStore/SAF support with graceful fallbacks
- UI Components: Replace single download button with dual-action interface
- Documentation: Add AndroidFileSaver plugin implementation guide
- Type Safety: Maintain interface consistency across all platform services
