Plex Connect: Ungroup player before starting playback (#2877)

Plex Connect: Ungroup player before starting playback (#2877)

* Plex Connect: Ungroup player before starting playback

When a user selects a specific player for playback in Plex, automatically
remove it from any sync groups or permanent groups. This improves UX by
ensuring playback only happens on the selected player, not all grouped players.

- Added _ungroup_player_if_needed() helper method
- Calls set_members directly to bypass static member restrictions
- Applied to handle_play_media (new playback) and handle_play (resume)
- Works with temporary syncs, permanent groups, and dynamic groups

* Plex Connect: Add error handling and feature checks to player ungrouping

* Plex Connect: implemented corrections