fix: remove all query suffix — rely on duration filter only

Adding 'audio' shifts results for lesser-known artists (Kanro, etc.).
Plain 'Artist - Title' matches what users find manually on YouTube.
Duration filter is the reliable quality check against wrong songs.

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

backend/novasonic-server.js

@@ -179,8 +179,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
   }
 
   const outputTemplate = path.join(dir, `${trackPrefix}${safeTitle}.%(ext)s`);
-  const isRemix = /\b(remix|edit|flip|vip|bootleg|mix|rework|cover)\b/i.test(title);
+  const query = `${mainArtist} - ${title}`;
-  const query   = isRemix ? `${mainArtist} - ${title}` : `${mainArtist} - ${title} audio`;
 
   // Step 1: yt-dlp — audio only, no thumbnail (we embed iTunes artwork ourselves)
   const baseArgs = [