hcloud replaces a server when user_data, image or ssh_keys change, and
cloud-init only runs at first boot anyway. An edit to cloud-init, like
adding a user, would therefore plan the destruction of a production
machine. Ignore changes to those three attributes and set
prevent_destroy on both servers, so cloud-init describes a rebuild and
nothing else.
Add user zerrtika to cloud-init to match the servers; the user was
created on them by playbook 04.
Assisted-by: Claude:fable-5-2
