Redesign tvOS player controls with centered transport cluster

- Move Close to a top-right circular icon; bottom row reorganizes into
  left (Settings/Info/Comments), center transport (Previous/PlayPause/Next),
  and right (Queue) clusters with equal side frames so transport stays
  geometrically centered.
- Introduce a circular icon-only `TVTransportButtonStyle` (primary variant
  for Play/Pause) mirroring the new Close button look.
- Always render Previous/Next so Play/Pause position is fixed; dim and
  disable when unavailable.
- Share `isTransportDisabled` on `PlayerState` and reuse it on iOS and
  tvOS; apply it (plus symbol replace transition) to the tvOS Play/Pause
  button.

Yattee/Views/Player/PlayerControlsView.swift

@@ -807,10 +807,7 @@ struct PlayerControlsView: View {
 
     /// Whether transport controls should be disabled (during loading/buffering or buffer not ready)
     private var isTransportDisabled: Bool {
-        playerState.playbackState == .loading ||
-        playerState.playbackState == .buffering ||
-        !playerState.isFirstFrameReady ||
-        !playerState.isBufferReady
+        playerState.isTransportDisabled
     }
 
     private var playPauseIcon: String {