Playback Report

Add support for client playback timeline reporting.

OpenSubsonic version: 1

OpenSubsonic extension name playbackReport (As returned by getOpenSubsonicExtensions)

When a server supports this extension, it provides the reportPlayback endpoint and can expose timeline fields in getNowPlaying responses.

Version 1

Clients can report playback status with mediaId, mediaType, positionMs, state, playbackRate, and ignoreScrobble.

When ignoreScrobble=true, the server should only update now playing display/state fields and should not perform playcount/scrobble side effects.