UI needs to implement a logout page/button/route

**Is your feature request related to a problem? Please describe.**
Right now there's no way for the admin to logout other than clear up the browser cookies, so we need a logout page to simply this process.

**Describe the solution you'd like**
A clear and concise description of what you want to happen.

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
Add any other context or screenshots about the feature request here.

The issue does not name any files, tests, or route entry points. Start by locating the admin UI's authentication and routing code, then determine the existing session or cookie behavior. Done means the admin has a usable logout page, button, or route that ends the current session without manually clearing browser cookies.

Written by the indexing model from the issue text.