fix: NP flicker, fully-random shuffle, playlist count backpatch

NP overlay flicker (stronger fix):
- Remove contain:layout style paint (causes layer issues on some Android WebView)
- Add ::before pseudo-element with solid background so no frame can be transparent
- Add -webkit-transform prefixes for both open and closed states

Shuffle fully random:
- playQueue no longer pins startIdx when shuffle is on
- All songs shuffled into a completely random order, S.qIdx=0 always
- toggleShuffle mid-queue still pins current song first (Spotify toggle behavior)

Playlist count wrong in overview:
- Navidrome's getPlaylists returns stale/wrong songCount in its index
- Add data-pl-id to each playlist card in loadPlaylists
- After loadPlaylistDetail gets the accurate entry count, backpatch the
  matching overview card's subtitle so the grid shows the real song count

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

src/player.js

@@ -359,13 +359,11 @@ export function playQueue(songs, startIdx) {
   _radioFilling = false; // cancel any in-flight radio fill for the old queue
   S._origQueue = null;
   _histClear();
-  // Spotify-style shuffle: build a fixed shuffled order once, pin the tapped song first.
-  // Applies to both web and Android — queue is traversed sequentially in this fixed order.
+  // Shuffle: fully random order, no pinning — startIdx is ignored.
+  // Both web and Android traverse this fixed shuffled order sequentially.
   if (S.shuffle && songs.length > 1) {
-    const start = songs[startIdx];
-    const rest  = songs.filter((_, i) => i !== startIdx).sort(() => Math.random() - 0.5);
     S._origQueue = songs.map(s => ({...s}));
-    S.queue = [start, ...rest].map(s => ({...s}));
+    S.queue = [...songs].sort(() => Math.random() - 0.5).map(s => ({...s}));
     S.qIdx  = 0;
   } else {
     S.queue = songs.map(s => ({...s}));