fix: case-insensitive title filter + scan before playlist creation

backend: replace title *= (case-sensitive) with title ~= (?i) regex so
"MEMORIES" and "Echoes of Eternity" match regardless of YT title casing.
Refactor buildTitleKeyword → buildTitleKeywords returning array.

frontend: trigger Navidrome startScan after download completes and wait
for scan to finish before running _createNdPlaylist, so newly downloaded
tracks are indexed and searchable when the playlist is built.

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

src/ui.js

@@ -344,6 +344,18 @@ async function _pollAndCreatePlaylist(jobId, tracks, playlistName) {
     if (!job || job.status === 'done' || job.status === 'error') break;
   }
   if (S.jobs[jobId]?.status !== 'done') return;
+
+  // Trigger Navidrome library scan so newly downloaded files are indexed before searching
+  try {
+    await api('startScan', '');
+    toast('🔍 Navidrome scannt Bibliothek…');
+    for (let i = 0; i < 90; i++) {
+      await new Promise(r => setTimeout(r, 2000));
+      const st = await api('getScanStatus', '');
+      if (!st?.scanStatus?.scanning) break;
+    }
+  } catch { /* scan API unavailable — proceed anyway */ }
+
   await _createNdPlaylist(tracks, playlistName);
 }