fix: load album art via local /art proxy instead of external URL

WebEngine blocks fetching external Spotify URLs from local content.
Now uses http://127.0.0.1:8765/art which proxies the image locally.

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

plugin/contents/ui/dancer.html

@@ -1055,27 +1055,15 @@ const albumArtEl = document.getElementById('albumArt');
 
 let lastArtUrl = '';
 
-function setAlbumArt(url) {
-  if (!url || url === lastArtUrl) return;
-  lastArtUrl = url;
-  fetch(url)
-    .then(r => r.blob())
-    .then(blob => {
-      const reader = new FileReader();
-      reader.onload = () => {
-        albumArtEl.style.backgroundImage = `url('${reader.result}')`;
-      };
-      reader.readAsDataURL(blob);
-    })
-    .catch(() => {});
-}
-
 function fetchTheme() {
   fetch('http://127.0.0.1:8765/current')
     .then(r => r.json())
     .then(d => {
       if (d.rgb) applyTheme(d.rgb);
-      if (d.art_url) setAlbumArt(d.art_url);
+      if (d.art_url && d.art_url !== lastArtUrl) {
+        lastArtUrl = d.art_url;
+        albumArtEl.style.backgroundImage = "url('http://127.0.0.1:8765/art')";
+      }
     })
     .catch(() => {});
 }