feat: wire SQLite replication between site nodes and fix ConfigurationDatabase tests

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.

src/ScadaLink.SiteRuntime/Messages/ReplicationMessages.cs

@@ -0,0 +1,34 @@
+using ScadaLink.Commons.Messages.Artifacts;
+using ScadaLink.StoreAndForward;
+
+namespace ScadaLink.SiteRuntime.Messages;
+
+/// <summary>
+/// Outbound messages — sent by local DeploymentManagerActor/S&amp;F service
+/// to the local SiteReplicationActor for forwarding to the peer node.
+/// </summary>
+public record ReplicateConfigDeploy(
+    string InstanceName, string ConfigJson, string DeploymentId, string RevisionHash, bool IsEnabled);
+
+public record ReplicateConfigRemove(string InstanceName);
+
+public record ReplicateConfigSetEnabled(string InstanceName, bool IsEnabled);
+
+public record ReplicateArtifacts(DeployArtifactsCommand Command);
+
+public record ReplicateStoreAndForward(ReplicationOperation Operation);
+
+/// <summary>
+/// Inbound messages — received from the peer's SiteReplicationActor
+/// and applied to local SQLite storage.
+/// </summary>
+public record ApplyConfigDeploy(
+    string InstanceName, string ConfigJson, string DeploymentId, string RevisionHash, bool IsEnabled);
+
+public record ApplyConfigRemove(string InstanceName);
+
+public record ApplyConfigSetEnabled(string InstanceName, bool IsEnabled);
+
+public record ApplyArtifacts(DeployArtifactsCommand Command);
+
+public record ApplyStoreAndForward(ReplicationOperation Operation);