Notification management UI

Implement the frontend to manage notifications in TMS.
Administrator users should be able to add, edit and delete notifications. A notification shall consist of the following information:

• Message;
• Start time to show the notification for users;
• End time to show the notification for users;
• Available to all users or only logged in users.

The notifications shall be visible as a horizontal bar on the top of the website. If a notification is available to all users, it should also be display on the login page.

Notifications should be dismissible by the users, so they do not show up anymore. This information does not need to be persisted to the backend, it could be stored in the browser.