Farcaster

feat: Add offline data support and network monitoring

- Added NetworkMonitor class to monitor network connectivity.
- Added isConnected property to CurrencyViewModel to check network status.
- Modified fetchRates method in CurrencyViewModel to use offline data when no internet connection is available.
- Added OfflineDataView to ContentView to notify users when they are viewing offline data.
- Displayed the last update time of the data in OfflineDataView.
- Updated ContentView to check and display offline data status.
- Improved error handling and user notifications.

https://vimeo.com/980035926

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