Expose Background Playback toggle on tvOS, default off

Surfaces the existing iOS/macOS Background Playback setting in the tvOS
Playback settings, defaulting to off so audio stops when the user leaves
the app via the TV button. Pauses playback on .background/.inactive when
the toggle is off, regardless of audio route — the user's setting wins
over AirPlay/HomePod handoff. Also auto-shows the tvOS player controls
when returning to foreground so the paused state is immediately visible
and actionable.

Yattee/Services/Player/PlayerService.swift

@@ -650,6 +650,15 @@ final class PlayerService {
         #else
         let isPiPActive = false
         #endif
+
+        #if os(tvOS)
+        LoggingService.shared.debug("PlayerService[tvOS-bg]: phase=\(phase) bgEnabled=\(backgroundEnabled) playbackState=\(state.playbackState)", category: .player)
+        if (phase == .background || phase == .inactive), !backgroundEnabled, state.playbackState == .playing {
+            LoggingService.shared.debug("PlayerService[tvOS-bg]: pausing playback (phase=\(phase), backgroundPlaybackEnabled=false)", category: .player)
+            pause()
+        }
+        #endif
+
         currentBackend?.handleScenePhase(phase, backgroundEnabled: backgroundEnabled, isPiPActive: isPiPActive)
     }