Add SiteReplicationActor (runs on every site node) to replicate deployed
configs and store-and-forward buffer operations to the standby peer via
cluster member discovery and fire-and-forget Tell. Wire ReplicationService
handler and pass replication actor to DeploymentManagerActor singleton.
Fix 5 pre-existing ConfigurationDatabase test failures: RowVersion NOT NULL
on SQLite, stale migration name assertion, and seed data count mismatch.
