Point DefaultInstance.SMTPConfiguration at the in-cluster smtp-gotify relay, so
verification codes and password resets arrive on the phone instead of being
dropped for lack of a mail path.
Validated with `helm template zitadel/zitadel 10.4.0` before syncing: the block
renders, and the zatadel-config-yaml ConfigMap is still produced. An earlier
attempt looked like it removed that ConfigMap, which is why this went in only
after a local render check.
rock
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