Save to Files: copy books, free audiobooks and Verse By Verse lessons and handouts into Seafile (background job, progress, skips what is there)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UaC9HmtHMdRP8dAbN4wAKj

books.js

@@ -144,4 +144,7 @@ async function handle(req, res) {
   return json(res, 404, { error: 'Not found' });
 }
 
-module.exports = { handle, mergeNotes, looksLike, addBook, index, TYPES };
+/** Where a book's file is on disk (for the signed-in person). */
+const fileOf = id => { const b = index().find(x => x.id === id); return b ? { path: path.join(dir(), id + '.' + b.ext), ext: b.ext, title: b.title, author: b.author } : null; };
+
+module.exports = { handle, mergeNotes, looksLike, addBook, index, TYPES, fileOf };