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>

index.html

@@ -663,6 +663,13 @@
           Theme
         </h3>
         <div id="theme-picker" class="theme-picker"></div>
+        <div class="edit-pl-toggle-row" style="margin-top:14px">
+          <div>
+            <span>Dynamische Hintergrundfarbe</span>
+            <div class="hint" style="margin-top:2px">Jetzt-Läuft-Hintergrund nach Cover-Hauptfarbe</div>
+          </div>
+          <div id="s-cover-color-bg" class="toggle" onclick="this.classList.toggle('on')"></div>
+        </div>
       </div>
     </div>
     <!-- Sticky footer -->