Don't expose pretty launch page to authenticated users

(I suspect you wanted this to view things as an admin, but if that's the case we should add it to an admin-only route!)
Filing this one under "who cares—have thousands of other way more important functionalities to consider."

If signed-in users REALLY want to see the homepage, why not let them? The UI won't show them by default, and there aren't any links to it, but it's absolutely non-harmful and it means I don't need to log in and out all the damned time.