fix: prevent 9-second downloads caused by short iTunes duration match

When iTunes enrichment returns a jingle/preview as the first result (e.g.
trackTimeMillis=9000), the yt-dlp duration filter becomes impossible
(duration > 30 & duration < 24), all filtered steps fail, and the final
unfiltered fallback downloads whatever YouTube returns first — often a
short clip.

Fix 1: spotify.js — only copy iTunes trackTimeMillis to durationMs when
it is > 30 seconds (genuine song, not a jingle or preview).

Fix 2: ytdlp.js — only enter the duration-filtered search branch when
durationMs > 30 000ms, so a corrupted short value silently falls back to
the unfiltered search path which still finds the correct full song.

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

src/spotify.js

@@ -305,7 +305,9 @@ async function _loadSpotifyTrackArtwork(tracks, listEl) {
           if (match.collectionName)   t.collectionName     = match.collectionName;
           if (match.releaseDate)      t.releaseDate        = match.releaseDate;
           if (match.trackNumber)      t.trackNumber        = match.trackNumber;
-          if (match.trackTimeMillis)  t.durationMs         = match.trackTimeMillis;
+          // Only use iTunes duration if it looks like a full song (> 30s) — jingles/previews
+          // returning a small trackTimeMillis would corrupt the yt-dlp duration filter.
+          if (match.trackTimeMillis > 30000) t.durationMs  = match.trackTimeMillis;
         }
         if (window._spotifyResolved?.tracks?.[idx]) Object.assign(window._spotifyResolved.tracks[idx], t);
         const url = match.artworkUrl100 || match.artworkUrl60 || '';