feat(player): channel list sidebar accessible from the live OSD

Add a visible playlist button in both players (native + lite) that opens
the TiviMate-style channel sidebar (channels of the current category).
The sidebar existed in the native player but was only reachable via an
edge swipe or the M/Menu key; the lite player had none.

- New OSD button next to channel zapping (live only)
- Lite player: full sidebar port (swipe from right edge, M/Menu key)
- D-pad support: focus lands on the current channel when the list opens,
  arrows navigate, OK switches channel, Back/Menu closes
- Auto-hide timer (6s) restarted on D-pad focus and touch scroll
- Bump version to 1.8.0+15

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EG1frWE7suYF7hp4q2sDiR

pubspec.yaml

@@ -1,7 +1,7 @@
 name: xtremobile
 description: High-performance IPTV Android Application with Xtream Codes API
 publish_to: 'none'
-version: 1.7.0+14
+version: 1.8.0+15
 
 environment:
   sdk: '>=3.0.0 <4.0.0'