- Add uniquePlaylistName method to auto-rename duplicate names with (1), (2), etc.
- Call uniquePlaylistName only from ImportPlaylist, not CreatePlaylist
- Update PlaylistFilePicker to return []string via OpenMultipleFilesDialog
- Add ImportPlaylists method for sequential batch import with partial success
- Queue.SetContext acquires existing q.mu before writing q.ctx
- Library struct gets new mu sync.Mutex; SetContext and SetRescanHooks acquire it
- Playlist Service struct gets new mu sync.Mutex; SetContext and SetFavoritesConfig acquire it
- Library and Playlist release lock before calling post-init methods (registerEventHandlers, migrateExistingPlaylists)
yonlu