fix: UI refinements for NowPlayingBar and QualityBadge

- Artwork preview only triggers on hover over artwork, not entire song-card
- Double song-card min-width (320px → 640px, max 700px)
- Reduce all control icons by 2px (18→16, 20→18, 22→20)
- Reduce control button sizes (32→30px, play 36→34px)
- QualityBadge: reduce text 1pt (9→8px, 10→9px), alpha 90%

src/lib/components/QualityBadge.svelte

@@ -133,16 +133,16 @@
   }
 
   .tier-label {
-    font-size: 9px;
+    font-size: 8px;
     font-weight: 600;
     text-transform: uppercase;
     letter-spacing: 0.5px;
-    color: rgba(255, 255, 255, 0.85);
+    color: rgba(255, 255, 255, 0.9);
   }
 
   .quality-info {
-    font-size: 10px;
+    font-size: 9px;
     font-weight: 500;
-    color: rgba(255, 255, 255, 0.85);
+    color: rgba(255, 255, 255, 0.9);
   }
 </style>