feat: player improvements — gestures, haptics, queue, lyrics & back-handling

[Ericgacoki]

A batch of player UX fixes and small features, verified on-device.

Player screen

• Pager commits the track change on release (settledPage) instead of at the 50% point — fixes premature/unwanted track switches.
• Seekbar seeks only on release; dragging no longer fires a flood of seek/API calls.
• Drag the mini-player down to dismiss: clears the queue (player + VM cache) with a vibrant haptic and an Undo snackbar (hosted at the app Scaffold so it stays visible after dismiss). Axis-based, so it doesn't clash with the prev/next swipe. (ref [Feature Request] Swipe on the mini player to close #68)
• Expanding the mini-player no longer auto-starts a paused track (replaced the racy play()/pause() seed on session reconnect with a direct state seed).
• Central soft haptic on committed actions (play/pause, next/prev, seek-release, shuffle, repeat, favorite).

Queue sheet

• Tapping the pinned now-playing closes the queue (exact reverse of the Queue icon); the player stays expanded.
• Reversing a downward drag to upward pulls the sheet back up instead of the tracks list capturing it.

Lyrics

• Reduced the progress-bar (divider) height.
• Long-press a lyric line to copy its text.

Back navigation

• With the player expanded over another screen, device Back minimizes the player (closing the queue first if open) instead of navigating the screen behind — the BackHandler is now registered after the NavHost so it wins.

Follow-up

• Migrate haptics off direct Vibrator calls to Compose's native HapticFeedback. (Refactor: delegate haptics to Compose's HapticFeedback instead of direct Vibrator calls #123)

[Ericgacoki]

Fixes #68