Improve Handling and Visibility of Logged-In-Status for Terminal

Goal is to prevent an admin being logged in where they shouldn't be logged in, and to prevent the login of an admin overriding the Terminal-Login. Plan is to:

1. visibly display the fact that an admin is logged in on the Start Page, if that is the case
2. saving the Terminal-token in a different cookie so that the terminal status isn't overwritten by an admin login
3. giving a short indicator that a terminal user is still logged in.