feat: artist cards navigate-only (no play); add Top Songs + Shuffle buttons to artist detail page

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

index.html

@@ -151,6 +151,7 @@
       <div class="page" id="page-artist-detail">
         <button class="back-btn" id="artist-back-btn"><svg width="13" height="13" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><polyline points="15 18 9 12 15 6"/></svg>Alle Künstler</button>
         <div class="artist-hero" id="artist-detail-hero"><div class="artist-hero-overlay"><div class="artist-hero-name" id="artist-detail-name"></div></div></div>
+        <div id="artist-action-bar" class="artist-action-bar"></div>
         <div id="artist-bio-section"></div>
         <div id="artist-similar-section"></div>
         <div id="artist-topsongs-section"></div>