Broken standby cluster links

https://pigsty.io/docs/patroni/standby_cluster/ has it's own page now, but some pages like https://pigsty.io/docs/pgsql/param/ still link to the obsolete https://pigsty.io/docs/pgsql/config#standby-cluster URL.

content/docs/pgsql/_index.md:- [Standby Cluster](/docs/pgsql/config#standby-cluster): Clone existing cluster and keep in sync (DR cluster)
content/docs/concept/iac/_index.md:as well as different clusters: such as [**standby clusters**](/docs/pgsql/config#standby-cluster), [**Citus clusters**](/docs/pgsql/config#citus-cluster), and even [**Redis**](/docs/redis) / [**MinIO**](/docs/minio) / [**Etcd**](/docs/etcd) clusters
content/docs/pgsql/param/_index.md:or even set up [standby clusters](/docs/pgsql/config#standby-cluster) and [delayed clusters](/docs/pgsql/config#delayed-cluster) to quickly respond to data loss caused by human errors and software defects.
content/docs/pgsql/param/_index.md:Upstream instance IP address for [standby cluster](/docs/pgsql/config#standby-cluster) or cascade replica.
content/docs/pgsql/param/_index.md:Setting `pg_upstream` on the `primary` instance of a cluster indicates this cluster is a [standby cluster](/docs/pgsql/config#standby-cluster), and this instance will act as a `standby leader`, receiving and applying changes from the upstream cluster.

Start with the three files named in the issue: content/docs/pgsql/_index.md, content/docs/concept/iac/_index.md, and content/docs/pgsql/param/_index.md. Review each obsolete /docs/pgsql/config#standby-cluster link and verify the replacement points to /docs/patroni/standby_cluster/. Done means the listed standby-cluster references no longer lead to the obsolete section.