fix: split multi-artists in player bar and now playing overlay, fix broken onclick

- player bar: fix onclick broken by JSON.stringify producing double-quoted strings inside double-quoted HTML attribute; use single-quoted JS args instead
- now playing overlay: np-artist-name now splits artists and each is individually clickable (closes NP then navigates to artist)
- remove wrapper onclick from both np-artist-name and player-artist-name in HTML

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

index.html

@@ -634,7 +634,7 @@
       <div class="np-text">
         <div class="np-title" id="np-title">Kein Titel</div>
         <div class="np-artist" id="np-artist">
-          <span id="np-artist-name" onclick="npGoArtist()" style="cursor:pointer">—</span><span id="np-album-sep" style="opacity:.5"> · </span><span id="np-album-name" onclick="npGoAlbum()" style="cursor:pointer;opacity:.8">—</span>
+          <span id="np-artist-name">—</span><span id="np-album-sep" style="opacity:.5"> · </span><span id="np-album-name" onclick="npGoAlbum()" style="cursor:pointer;opacity:.8">—</span>
         </div>
       </div>
       <button class="np-star" id="np-star-btn" onclick="npToggleStar()">