feat: dynamic NP cover color, taller settings modal, fix Android song sync

- Now Playing: add "Dynamische Hintergrundfarbe" toggle in Theme settings;
  when on, np-bg uses higher saturation/brightness so the cover color really
  shows through the blurred background
- Settings modal: extend to bottom nav on mobile (was leaving ~74px dead space
  for the player bar which the overlay already covers at z-index 200)
- Android: fix onTrackChanged always staying on the first song — the snapshot
  from MediaController can lag behind ExoPlayer on auto-advance, causing the
  stale currentIndex to overwrite the correct p.index; now only advance to
  a higher live index (for rapid-skip catch-up) and use p.trackId directly
  instead of the potentially-stale snapshot id for the queue-mismatch guard

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main.js

@@ -9,7 +9,7 @@ import {
   initProgressScrub, updateProgress, updatePreviewProgress, stopPreview,
   toggleRadioMode, starCurrent, downloadCurrent, renderQueue, playPreview,
   toggleStar, dlSongLocal, _applyRadioBtn, _applyShuffleRepeat, _restoreLastPlayed, setPlayIcon,
-  npToggleStar, updateMediaSession,
+  npToggleStar, updateMediaSession, updateNpColorMode,
 } from './player.js';
 import {
   navigate, _navGoBack, _navLoad, onHeaderSearch, closeHeaderSearch,
@@ -125,6 +125,7 @@ window.addEventListener('load', () => {
     S.cfg = JSON.parse(saved);
     if(!S.cfg.backendUrl && window.NS_BACKEND_URL?.trim()) S.cfg.backendUrl = window.NS_BACKEND_URL.trim().replace(/\/$/,'');
     startApp();
+    updateNpColorMode();
   }
   if(window.NS_SERVER_URL?.trim()) { const el=document.getElementById('srv-url'); if(el&&!el.value) el.value=window.NS_SERVER_URL.trim(); }