fix: correct yt-dlp duration filter — handle exit code 101, remove --playlist-items from filtered search

--playlist-items 1 in baseArgs caused filter to only check result #1 (filter useless).
--max-downloads 1 exits with code 101 which we treated as an error — ffmpeg never ran,
leaving untagged files (→ Unknown Artist/Album in Navidrome). Now code 101 resolves
successfully and filtered search uses commonArgs without --playlist-items.

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

backend/novasonic-server.js

@@ -182,16 +182,16 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
   const query          = `${mainArtist} - ${title} official audio`;
 
   // Step 1: yt-dlp — audio only, no thumbnail (we embed iTunes artwork ourselves)
-  const baseArgs = [
+  const commonArgs = [
     '--extract-audio',
     '--audio-format',   CONFIG.audioFmt,
     '--audio-quality',  CONFIG.audioQuality,
     '-o',               outputTemplate,
-    '--no-playlist',
-    '--playlist-items', '1',
     '--no-warnings',
     '--newline',
   ];
+  // --no-playlist + --playlist-items 1 only for single-result searches (prevents playlist bleed)
+  const singleArgs = [...commonArgs, '--no-playlist', '--playlist-items', '1'];
 
   const spawnYtdlp = (args) => new Promise((resolve, reject) => {
     const proc = spawn(CONFIG.ytdlpBin, args, { env: { ...process.env, PYTHONUNBUFFERED: '1' } });
@@ -210,8 +210,9 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
         .forEach(l => log(jobId, l.trim()));
     });
     proc.on('error', reject);
+    // code 101 = --max-downloads limit reached (success — file was downloaded)
     proc.on('close', code =>
-      code === 0 ? resolve() : reject(new Error(`yt-dlp code ${code}: ${stderr.slice(-300)}`))
+      (code === 0 || code === 101) ? resolve() : reject(new Error(`yt-dlp code ${code}: ${stderr.slice(-300)}`))
     );
   });
 
@@ -220,21 +221,22 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
     const minDur = Math.max(30, Math.round(durationSec * 0.6));
     const maxDur = Math.round(durationSec * 1.5);
     log(jobId, `🔍 Suche (~${durationSec}s): "${query}"`);
+    // Search 5 results, pick first matching duration — no --playlist-items so filter sees all 5
     await spawnYtdlp([
       `ytsearch5:${query}`,
       '--match-filter', `duration > ${minDur} & duration < ${maxDur} & !is_live`,
       '--max-downloads', '1',
-      ...baseArgs,
+      ...commonArgs,
     ]);
     // Fallback if duration filter matched nothing
     const hasFile = fs.readdirSync(dir).some(f => AUDIO_EXTS.some(e => f.endsWith(`.${e}`)));
     if (!hasFile) {
       log(jobId, '⚠️  Kein Treffer im Dauerbereich — Suche ohne Filter…');
-      await spawnYtdlp([`ytsearch1:${query}`, ...baseArgs]);
+      await spawnYtdlp([`ytsearch1:${query}`, ...singleArgs]);
     }
   } else {
     log(jobId, `🔍 Suche: "${query}"`);
-    await spawnYtdlp([`ytsearch1:${query}`, ...baseArgs]);
+    await spawnYtdlp([`ytsearch1:${query}`, ...singleArgs]);
   }
 
   // Step 2: find the audio file yt-dlp wrote (newest audio file in dir)