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
`Session.uid` is only stored in `sessionStorage`, so there could be a case where you end up on the `confirm` page without a `uid` in `Session`. The only flow that allows this ACAICT is the "resend verification email" link from the change password flow.