feat(sync): refactor Nextcloud sync script with retries and argument
handling
- Add centralized sync_directory() function
- Add retry logic with configurable attempts and delay
- Improve argument parsing and help output
- Add validation for selected sync targets
- Add support for sync marker removal (-del)
- Add logging abstraction with silent/live output modes
- Add dependency and credential file checks
- Prevent concurrent nextcloudcmd executions
- Improve error handling and script structure
- Add version flag support
- Standardize synchronization workflow for all folders
asd
