Store: one tab combining books, free audiobooks and radio, plus My Store for your own books, music, apps and sandboxed extensions

- Store tab with sections; the book store, LibriVox and radio finder are shown inside it (old entry points redirect)
- My Store: admin uploads files or copies from Seafile; books go to a person's shelf, music plays in the player, apps download
- Extensions: one HTML file run in a sandboxed frame with a small storage/toast/user bridge; example in docs/extensions

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

package.json

@@ -5,7 +5,7 @@
   "main": "server.js",
   "scripts": {
     "start": "node server.js",
-    "test": "for t in smoke tasks push users cal plex player lyrics signal mail mail-imap files podcast abapi abdirect books store librivox radio vbv savefiles bible lrclib visualizer body transcript recipes contacts; do node tools/$t-test.js || exit 1; done",
+    "test": "for t in smoke tasks push users cal plex player lyrics signal mail mail-imap files podcast abapi abdirect books store librivox radio vbv savefiles bible lrclib visualizer body transcript recipes contacts mystore; do node tools/$t-test.js || exit 1; done",
     "audit": "npm audit --omit=dev --audit-level=high"
   },
   "keywords": [],