fix: export App as named notificationsApp

Matches the learner-dashboard pattern. Drops the other re-exports,
since they were originally meant for backward compatibility, but
that turned out not to be possible.

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

Author: arbrandes

src/index.ts

@@ -1,4 +1 @@
-export { default } from './app';
-export { default as NotificationsTray } from './NotificationsTray';
-export { default as Notifications } from './Notification';
-export { useAppNotifications, useNotification } from './Notification/data/hook';
+export { default as notificationsApp } from './app';