fix: install yt-dlp via pip3 for latest version, fix multi-artist folder path

- Replace apk yt-dlp with pip3 install to get current version with ytmsearch support
- Split mainArtist on comma in downloadTrack so multi-artist tracks
  always land in the primary artist folder (e.g. "Artist1, Artist2" → Artist1/)

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

backend/novasonic-server.js

@@ -163,7 +163,8 @@ async function lookupItunesTrackMeta(artist, title) {
 // Download a single track: yt-dlp audio + ffmpeg clean metadata + iTunes cover embedded
 async function downloadTrack({ jobId, artist, albumArtist, title, album, year, trackNum, totalTracks, discNum, discTotal, durationMs, compilation, genre, artworkUrl, explicit, outputDir }) {
   const mainArtist = albumArtist || artist;
-  const safeArtist = sanitize(mainArtist);
+  // use only the first artist for the folder path (e.g. "Artist1, Artist2" → "Artist1")
+  const safeArtist = sanitize(mainArtist.split(',')[0].trim());
   const safeAlbum  = sanitize(album || 'Singles');
   const dir = path.join(outputDir || CONFIG.musicPath, safeArtist, safeAlbum);
   fs.mkdirSync(dir, { recursive: true });

docker-compose.yml

@@ -30,7 +30,8 @@ services:
       - MAX_PARALLEL=${MAX_PARALLEL:-2}
     command: >
       sh -c "
-        apk add --no-cache yt-dlp ffmpeg python3 &&
+        apk add --no-cache ffmpeg python3 py3-pip &&
+        pip3 install -U yt-dlp --break-system-packages &&
         npm install express cors &&
         node novasonic-server.js
       "