Sprint 2

feat: add smoke tests for notifications persistence

- Implemented smoke tests in `smoke_notifications.fish` to verify the notification system's functionality, including user registration, application submission, notification retrieval, and read status updates.
- Created a new repository for notifications in `notifications.repo.ts` with functions to create, list, and mark notifications as read.
- Defined notification types in `notifications.types.ts` for better type safety and clarity in the notification handling process.