🚀 refactor(pmocontrol): eliminate QueueBackend boilerplate with HasQueue blanket impl

- Add `Hasqueue` trait and implement it for all renderers (Upnp, OpenHome, LinkPlay, ArylicTcp, Chromecast)
- Replace manual `QueueBackend` implementations with blanket impl for types implementing Hasqueue
  (removes ~30+ duplicated methods across renderers)
- Fix BUG: `sync_queue` in UpnpRenderer now correctly propagates cancel_token instead of ignoring it
- Update version to 0.3.48 in Cargo.toml, lockfile and root file
- Add refactoring plan document (`refactoring_pmocontrol.md`) detailing remaining P1-P3 tasks

pmocontrol/src/queue/mod.rs

@@ -6,7 +6,7 @@ mod snapshot;
 
 use std::sync::{Arc, Mutex};
 
-pub use backend::{EnqueueMode, QueueBackend};
+pub use backend::{EnqueueMode, HasQueue, QueueBackend};
 pub use music_queue::{MusicQueue, SyncScheduleOutcome};
 pub use snapshot::{PlaybackItem, QueueSnapshot};