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/lib/ytdlp.js

@@ -54,16 +54,20 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
   const dir = path.join(outputDir || CONFIG.musicPath, safeArtist, safeAlbum);
   fs.mkdirSync(dir, { recursive: true });
 
-  const safeTitle   = sanitize(title);
-  const trackPrefix = trackNum ? String(trackNum).padStart(2, '0') + ' - ' : '';
+  const safeTitle        = sanitize(title);
+  const trackPrefix      = trackNum ? String(trackNum).padStart(2, '0') + ' - ' : '';
+  // Filename format: "{01 - }Artist1, Artist2 - Title.ext"
+  // Use track artist (not albumArtist) so all credited artists appear in the filename
+  const safeArtistForFile = sanitize(artist.replace(/;/g, ','));
+  const fileBase          = `${trackPrefix}${safeArtistForFile} - ${safeTitle}`;
 
-  const existing = findExistingTrack(dir, trackPrefix, safeTitle);
+  const existing = findExistingTrack(dir, trackPrefix, safeTitle, safeArtistForFile);
   if (existing) {
     log(jobId, `⏭ Bereits vorhanden: ${path.basename(existing)} — übersprungen`);
     return { success: true, dir, skipped: true };
   }
 
-  const outputTemplate = path.join(dir, `${trackPrefix}${safeTitle}.%(ext)s`);
+  const outputTemplate = path.join(dir, `${fileBase}.%(ext)s`);
   // Strip only Unicode symbol chars (☆ ★ ♥ etc.) for ytsearch — YouTube search chokes on them
   // and returns 0 results. Keep ASCII punctuation (!&-) so e.g. "N!GHT" stays "N!GHT" rather
   // than collapsing to "NGHT" which YouTube misreads as the word "night".
@@ -106,7 +110,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
   // Use original artist name (with special chars) for YTM URL — better search ranking than stripped version
   const ytmQuery = `${mainArtist} - ${title}`;
   const ytmUrl = `https://music.youtube.com/search?q=${encodeURIComponent(ytmQuery)}&params=${YTM_SONGS_PARAM}`;
-  const expectedAudio = path.join(dir, `${trackPrefix}${safeTitle}.${CONFIG.audioFmt}`);
+  const expectedAudio = path.join(dir, `${fileBase}.${CONFIG.audioFmt}`);
   const hasAudio = () => fs.existsSync(expectedAudio);
 
   // Direct URL download (e.g. SoundCloud) — skip the ytsearch cascade entirely