SDP review fixes: replication topology & failover
mkstandby.sh: fix unterminated sed (default standby never converted) + ReplicationFrom
typo + mktemp for service-user password. mkstandby_shared.sh: derive ReplicatingFrom from
P4MASTER_ID not P4MASTERPORT. convert_standby_to_master.sh: validate recovery journal
before deleting the live journal. No errexit added.