fix: smooth NP swipe-open animation; live playing highlight in song lists

Swipe animation:
- _resetDrag(true) now reads the overlay's current drag position and starts
  the CSS transition from there instead of resetting to translateY(100%) first.
  That reset was causing the visible stutter (overlay jumped off-screen then
  slid back up). Now the overlay continues seamlessly from wherever the finger
  released to translateY(0).

Playing highlight:
- makeSongItem: adds data-song-id attribute to every .song-item element.
- updatePlayerUI: calls _updatePlayingHighlights() after every track change.
  This toggles .playing on all visible song items in any open list/playlist/
  favorites view so the highlighted row always matches what's actually playing,
  without requiring the user to navigate away and back.

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

src/components.js

@@ -31,6 +31,7 @@ export function makeSongItem(s, idx, list, { noArtistLink = false, noAlbumLink =
   const el = document.createElement('div');
   if(s.starred && !s._starred) s._starred = true;
   el.className = 'song-item' + (S.queue[S.qIdx]?.id === s.id ? ' playing' : '');
+  el.dataset.songId = s.id;
   const cv = coverUrl(s.coverArt, 128);
   const artistParts = (s.artist || '').split(/\s*(?:\/|•|,)\s*/).filter(Boolean);
   const artistHtml = artistParts.length