Handle refresh failures and session expiration more gracefully

[alexashley]

Right now if we fail to perform the refresh flow, we'll try to send the user through the login flow again.

This works if the user happens to be requesting a new page or refreshes, but doesn't play nicely when they're trying to interact with the current page. None of the calls we make on the front-end understand that redirect, but ideally we'd show a toast notification that prompts them to reauthenticate.