Audiobooks: built-in library, playback and synced progress through the audiobook player (classic frame kept)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/index.html

@@ -70,6 +70,7 @@
 <script src="/video.js"></script>
 <script src="/office.js"></script>
 <script src="/player.js"></script>
+<script src="/audiobooks-view.js"></script>
 <script src="/lyrics-view.js"></script>
 <script src="/settings.js"></script>
 <script src="/files.js"></script>