Fixed 5 critical gaps in the download orchestrator where lidarr was
missing from client loops: get_all_downloads, get_download_status,
cancel_download fallback, clear_all_completed_downloads, and
cancel_all_downloads. Without these, lidarr downloads were invisible
to the UI, couldn't be cancelled, and accumulated in memory.
Also: error messages now visible in download list (appended to
filename on error state), removed "(Development)" label from UI.
Lidarr integration:
- New core/lidarr_download_client.py with full interface parity
(search, download, status, cancel — same as Qobuz/Tidal/HiFi)
- Registered in download orchestrator with source routing
- Settings: URL + API key on Downloads tab with connection test
- Available as standalone source or in Hybrid mode priority order
- API key encrypted at rest
- All streaming source checks updated to include 'lidarr'
Lidarr downloads full albums via Usenet/torrent — SoulSync imports
only the tracks it needs and discards the rest.
Music video path validation:
- Empty/unconfigured path returns clear error instead of silent failure
- Write permission test before starting download
- Default changed from './MusicVideos' to empty (must be configured)
