feat: add settings option to hide Live TV categories (#11)

Add a liveChannelListMode setting (default 'grouped') with a Settings
toggle to display the Live TV channel list flat, without category
group sections. When enabled, logical channels are listed directly
with their stream variants still grouped as in #9/#10. Cover the
setting default and flat-list behavior with tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/js/components/VideoPlayer.js

@@ -57,6 +57,7 @@ class VideoPlayer {
             rememberVolume: true,
             lastVolume: 80,
             autoPlayNextEpisode: false,
+            liveChannelListMode: 'grouped',
             forceProxy: false,
             forceTranscode: false,
             forceRemux: false,
@@ -94,6 +95,7 @@ class VideoPlayer {
             const serverSettings = await API.settings.get();
             this.settings = { ...this.getDefaultSettings(), ...serverSettings };
             this.settingsLoaded = true;
+            window.app?.channelList?.setListMode(this.settings.liveChannelListMode);
             console.log('[Player] Settings loaded from server');
         } catch (err) {
             console.warn('[Player] Failed to load settings from server, using defaults:', err.message);