refactor: remove dead code from backend and lib

- Remove unused spotifyClientId/spotifyClientSecret from config
- Remove AUDIO_EXTS from metadata exports (internal-only)
- Remove tryYtdlp wrapper in ytdlp.js (direct spawnYtdlp calls)
- Remove _spArtistName wrapper in server (direct _spAllArtists calls)
- Fix stale comment: primary resolver is SpotipyFree, not curl_cffi

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

backend/lib/config.js

@@ -9,9 +9,6 @@ const CONFIG = {
   downloadBackend: (process.env.DOWNLOAD_BACKEND || 'auto').toLowerCase(),
   // squid.wtf quality: 'mp3' | 'flac' | 'hi-res'
   squidQuality:    (process.env.SQUID_QUALITY   || 'mp3').toLowerCase(),
-  // Spotify Developer credentials (Client Credentials Flow — free, no Premium needed)
-  spotifyClientId:     process.env.SPOTIFY_CLIENT_ID     || '',
-  spotifyClientSecret: process.env.SPOTIFY_CLIENT_SECRET || '',
 };
 
 module.exports = CONFIG;

backend/lib/metadata.js

@@ -138,6 +138,6 @@ async function searchItunesAlbumTracks(artist, album) {
 
 module.exports = {
   sanitize, navidromeArtist,
-  downloadArtwork, AUDIO_EXTS, findExistingTrack,
+  downloadArtwork, findExistingTrack,
   fetchLyrics, lookupItunesTrackMeta, fetchItunesTracks, searchItunesAlbumTracks,
 };

backend/lib/ytdlp.js

@@ -108,7 +108,6 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
   const ytmUrl = `https://music.youtube.com/search?q=${encodeURIComponent(ytmQuery)}&params=${YTM_SONGS_PARAM}`;
   const expectedAudio = path.join(dir, `${trackPrefix}${safeTitle}.${CONFIG.audioFmt}`);
   const hasAudio = () => fs.existsSync(expectedAudio);
-  const tryYtdlp = async (args) => { await spawnYtdlp(args); };
 
   // Fetch YTM search result URLs as a flat list (no channel expansion) and return only
   // actual video URLs (watch?v=…). This prevents yt-dlp from following an artist channel
@@ -152,7 +151,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
   const tryYtmSearch = async (maxItems, mfArgs) => {
     const urls = await getYtmVideoUrls(maxItems);
     if (!urls.length) return;
-    await tryYtdlp([...urls, '--max-downloads', '1', ...mfArgs, ...baseArgs]);
+    await spawnYtdlp([...urls, '--max-downloads', '1', ...mfArgs, ...baseArgs]);
   };
 
   const variantFilter = buildVariantFilter(title);
@@ -189,7 +188,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
     if (!hasAudio()) {
       // 2. YT top-5 — strict: same filters including channel check
       log(jobId, '⚠️  Kein YTM-Treffer — Fallback zu YouTube…');
-      await tryYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(dur, true, true), ...baseArgs]);
+      await spawnYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(dur, true, true), ...baseArgs]);
     }
     if (!hasAudio()) {
       // 3. YTM top-10 — no channel check (label channels, etc.)
@@ -198,7 +197,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
     }
     if (!hasAudio()) {
       // 4. YT top-10 — no channel check
-      await tryYtdlp([`ytsearch10:${query}`, ...PI_FILTERED_10, ...mf(dur, true), ...baseArgs]);
+      await spawnYtdlp([`ytsearch10:${query}`, ...PI_FILTERED_10, ...mf(dur, true), ...baseArgs]);
     }
     if (!hasAudio()) {
       // 5. YTM top-5 — no duration check
@@ -207,7 +206,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
     }
     if (!hasAudio()) {
       // 6. YT top-5 — no duration check
-      await tryYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(null, true), ...baseArgs]);
+      await spawnYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(null, true), ...baseArgs]);
     }
     if (!hasAudio()) {
       // 7. YTM top-5 — title only (no variant filter)
@@ -216,7 +215,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
     }
     if (!hasAudio()) {
       // 8. YT top-5 — title only
-      await tryYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(null, false), ...baseArgs]);
+      await spawnYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(null, false), ...baseArgs]);
     }
     if (!hasAudio()) {
       // 9. YTM — no filter at all, take first video result
@@ -225,7 +224,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
     }
     if (!hasAudio()) {
       // 10. YT — no filter
-      await tryYtdlp([`ytsearch1:${query}`, ...PI_UNFILTERED, ...baseArgs]);
+      await spawnYtdlp([`ytsearch1:${query}`, ...PI_UNFILTERED, ...baseArgs]);
     }
   } else {
     log(jobId, `🔍 Suche YT Music: "${query}"`);
@@ -233,7 +232,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
     await tryYtmSearch(5, mf(null, true, true));
     if (!hasAudio()) {
       // 2. YT top-5 — strict
-      await tryYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(null, true, true), ...baseArgs]);
+      await spawnYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(null, true, true), ...baseArgs]);
     }
     if (!hasAudio()) {
       // 3. YTM top-5 — no channel check
@@ -241,7 +240,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
     }
     if (!hasAudio()) {
       // 4. YT top-5 — no channel check
-      await tryYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(null, true), ...baseArgs]);
+      await spawnYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(null, true), ...baseArgs]);
     }
     if (!hasAudio()) {
       // 5. YTM top-5 — title only
@@ -250,7 +249,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
     }
     if (!hasAudio()) {
       // 6. YT top-5 — title only
-      await tryYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(null, false), ...baseArgs]);
+      await spawnYtdlp([`ytsearch5:${query}`, ...PI_FILTERED, ...mf(null, false), ...baseArgs]);
     }
     if (!hasAudio()) {
       // 7. YTM — first video result, no filter
@@ -259,7 +258,7 @@ async function downloadTrack({ jobId, artist, albumArtist, title, album, year, t
     }
     if (!hasAudio()) {
       // 8. YT — no filter
-      await tryYtdlp([`ytsearch1:${query}`, ...PI_UNFILTERED, ...baseArgs]);
+      await spawnYtdlp([`ytsearch1:${query}`, ...PI_UNFILTERED, ...baseArgs]);
     }
   }