fix: send track/disc numbers from iTunes to backend; backend reads them for single track downloads

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

backend/novasonic-server.js

@@ -564,7 +564,8 @@ app.post('/api/spotify/resolve', async (req, res) => {
 });
 
 app.post('/api/download', async (req, res) => {
-  const { type, artist, title, album, artworkUrl, collectionId, jobId: clientJobId, explicit } = req.body;
+  const { type, artist, title, album, artworkUrl, collectionId, jobId: clientJobId, explicit,
+          trackNum: bodyTrackNum, totalTracks: bodyTotalTracks, discNum: bodyDiscNum, discTotal: bodyDiscTotal } = req.body;
   if (!artist || !title) return res.status(400).json({ error: 'artist and title required' });
 
   const jobId = clientJobId || ('job_' + Date.now());
@@ -584,7 +585,11 @@ app.post('/api/download', async (req, res) => {
         const spAlbum = sp.collectionName || album || '';
         const spArt   = sp.artworkUrl100 || artworkUrl || '';
         const spYear  = sp.releaseDate ? new Date(sp.releaseDate).getFullYear() : undefined;
-        let meta = { album: spAlbum, year: spYear, trackNum: sp.trackNumber || undefined,
+        let meta = { album: spAlbum, year: spYear,
+          trackNum:    sp.trackNumber  || bodyTrackNum    || undefined,
+          totalTracks: sp.trackCount   || bodyTotalTracks || undefined,
+          discNum:     sp.discNumber   || bodyDiscNum     || undefined,
+          discTotal:   sp.discCount    || bodyDiscTotal   || undefined,
           artworkUrl: spArt, explicit: sp.trackExplicitness === 'explicit' || !!explicit };
         if (!meta.album) {
           // Use first artist only for iTunes search (multi-artist strings like "Kløn, Renzyx" confuse iTunes)

src/ui.js

@@ -294,6 +294,10 @@ export async function executeDownload() {
     itunesId:    S.downloadTarget.trackId || S.downloadTarget.collectionId || null,
     collectionId: S.downloadTarget.collectionId || null,
     explicit:    S.downloadTarget.trackExplicitness === 'explicit',
+    trackNum:    S.downloadTarget.trackNumber  || undefined,
+    totalTracks: S.downloadTarget.trackCount   || undefined,
+    discNum:     S.downloadTarget.discNumber   || undefined,
+    discTotal:   S.downloadTarget.discCount    || undefined,
   };
   addJob(jobId, payload.title, payload.artist, payload.type);
   try {