feat: artist in filename, hide album=title subtitle, remove title hover

Naming convention (download + edit-metadata):
  Before: {01 - }Title.ext
  After:  {01 - }Artist1, Artist2 - Title.ext
- ytdlp.js: builds fileBase with artist prefix; findExistingTrack checks
  both new and old format so existing files aren't re-downloaded
- metadata.js: findExistingTrack accepts optional safeArtist param
- novasonic-server.js: file rename on title edit now includes artist
  (falls back to Navidrome's stored artist if not provided in body)

Song list subtitle: hide album name when album === title (singles where
the album is named after the track appear to duplicate the title)

Player bar: removed .player-title:hover underline/colour effect

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

backend/novasonic-server.js

@@ -604,7 +604,8 @@ app.post('/api/edit-metadata', async (req, res) => {
     const ndApi  = `${ndUrl}/rest/getSong?id=${songId}&u=${encodeURIComponent(user)}&t=${token}&s=${salt}&v=1.16.1&c=novasonic&f=json`;
     const ndRes  = await fetch(ndApi, { signal: AbortSignal.timeout(8000) });
     const ndData = await ndRes.json();
-    filePath = ndData?.['subsonic-response']?.song?.path;
+    const ndSong = ndData?.['subsonic-response']?.song;
+    filePath = ndSong?.path;
     if (!filePath) return res.status(404).json({ error: 'Song not found in Navidrome' });
   } catch (e) {
     return res.status(502).json({ error: `Navidrome lookup failed: ${e.message}` });
@@ -687,12 +688,14 @@ app.post('/api/edit-metadata', async (req, res) => {
     // ── Post-save: rename file and/or move to correct artist/album folder ──
     let currentFile = filePath;
 
-    // 1. Rename file if title changed — convention: {01 - }?{sanitized title}.ext
+    // 1. Rename file if title changed — convention: {01 - }?{Artist} - {Title}.ext
     if (title) {
-      const safeTitle  = sanitize(title);
-      const prefix     = trackNum ? String(trackNum).padStart(2, '0') + ' - ' : '';
-      const newName    = `${prefix}${safeTitle}${fileExt}`;
-      const newPath    = path.join(path.dirname(currentFile), newName);
+      const safeTitle      = sanitize(title);
+      const fileArtist     = (artist || ndSong?.artist || '').replace(/;/g, ',');
+      const safeArtistPart = fileArtist ? sanitize(fileArtist) + ' - ' : '';
+      const prefix         = trackNum ? String(trackNum).padStart(2, '0') + ' - ' : '';
+      const newName        = `${prefix}${safeArtistPart}${safeTitle}${fileExt}`;
+      const newPath        = path.join(path.dirname(currentFile), newName);
       if (newPath !== currentFile && !fs.existsSync(newPath)) {
         try { fs.renameSync(currentFile, newPath); currentFile = newPath; }
         catch (e) { console.error('[edit-metadata] file rename:', e.message); }