- Create BaseViewModel to encapsulate common UI state (isLoading) and logic (toasts, finishing activity).
- Implement ViewModelEvent and BaseViewModelEvent for standardized UI communication via SideEffects.
- Move core business logic (I/O, Zip, WebDAV) from BackupActivity to BackupViewModel.
- Standardize code naming conventions and update documentation to English.
- Improve Activity purity by delegating state management and background tasks to the ViewModel.