fix(auditlog): populate the Actor column on outbound and central rows

Per the Audit Log Actor-column spec, Actor should carry the calling script
identity on outbound rows (ApiCall, DbWrite, NotifySend) and a system identity
on central-dispatch rows (NotifyDeliver). The original emission code hard-coded
Actor=null at all four sites, so only Inbound API rows (API key name) ever
filled it. Stamp the script identity and 'system' respectively.

tests/ScadaLink.SiteRuntime.Tests/Scripts/DatabaseSyncEmissionTests.cs

@@ -266,7 +266,8 @@ public class DatabaseSyncEmissionTests
         Assert.Equal(SiteId, evt.SourceSiteId);
         Assert.Equal(InstanceName, evt.SourceInstanceId);
         Assert.Equal(SourceScript, evt.SourceScript);
-        Assert.Null(evt.Actor);
+        // Outbound channel: Actor carries the calling script identity.
+        Assert.Equal(SourceScript, evt.Actor);
         Assert.Null(evt.CorrelationId);
         Assert.NotEqual(Guid.Empty, evt.EventId);
     }