feat(client): Allow the user to restart the signup flow on email bounce.

feat(client): Allow the user to restart the signup flow on email bounce.

Add two new error codes:
* 1018 - SIGNUP_EMAIL_BOUNCE
* 1019 - DIFFERENT_EMAIL_REQUIRED

fixes #1801
Should be rare to hit this, but it could happen. As it stands, the user will still see "Invalid token", but if the account still exists at this point, we should probably direct them to the login page and ask them to log in again.