Improve client-side error messages

[evan10s]

We have a lot of places with a generic error message with very little info. There are certain times (e.g., network errors) where it makes sense to show more info because we can't report the error to Sentry. It would be especially good to do this on the kiosk, which doesn't even show a different error when its PAT has expired. There are other places on the frontend where this might also be good to improve.

Also, on network errors (offline), consider adding automatic retries with exponential backoff.