Use local Unix domain socket connection for password sync

Instead of trying to use a superuser connection, the operator could exec psql in database pods to sync passwords, which would use a local connection through the PostgreSQL Unix domain socket. This would allow the operator to sync passwords even if the superuser secret is not consistent with a running cluster's state, which in turn would remove the need to preserve secrets upon cluster deletion, and simplify the process of restoring backups.

This may have a very low priority as the current workaround of not deleting secrets is effective.

Start by examining the password-sync entry point and how Kubernetes exec invokes psql in database pods. Verify the local PostgreSQL Unix domain socket approach against the existing superuser connection and secret-handling flow. Done means passwords sync without the superuser secret being consistent or preserved after cluster deletion, with backup restoration still working.