fix(site-event-log): record script errors and route queries to the active node

Script execution failures were only written to Serilog, never to the
site event log — SiteRuntime did not reference the SiteEventLogging
project. ScriptExecutionActor now resolves ISiteEventLogger and emits a
'script'/'Error' event on timeout and exception.

The event-log query handler was a per-node actor bound to that node's
local SQLite. A ClusterClient query could land on the standby (which
records no events) and return nothing. The handler is now a cluster
singleton with a proxy, so queries always reach the active node.

src/ScadaLink.Host/Actors/AkkaHostedService.cs

@@ -306,14 +306,29 @@ akka {{
         // Register local handlers with SiteCommunicationActor
         siteCommActor.Tell(new RegisterLocalHandler(LocalHandlerType.Artifacts, dmProxy));
 
-        // Event log handler — bridges Akka to IEventLogQueryService
+        // Event log handler — cluster singleton so queries always reach the
+        // active node. The event log is node-local SQLite and is not
+        // replicated; only the active node records events. A per-node handler
+        // would let a ClusterClient query land on the standby and find nothing.
         var eventLogQueryService = _serviceProvider.GetService<SiteEventLogging.IEventLogQueryService>();
         if (eventLogQueryService != null)
         {
-            var eventLogHandler = _actorSystem.ActorOf(
-                Props.Create(() => new SiteEventLogging.EventLogHandlerActor(eventLogQueryService)),
-                "event-log-handler");
-            siteCommActor.Tell(new RegisterLocalHandler(LocalHandlerType.EventLog, eventLogHandler));
+            var eventLogSingletonProps = ClusterSingletonManager.Props(
+                singletonProps: Props.Create(() => new SiteEventLogging.EventLogHandlerActor(eventLogQueryService)),
+                terminationMessage: PoisonPill.Instance,
+                settings: ClusterSingletonManagerSettings.Create(_actorSystem)
+                    .WithRole(siteRole)
+                    .WithSingletonName("event-log-handler"));
+            _actorSystem.ActorOf(eventLogSingletonProps, "event-log-handler-singleton");
+
+            var eventLogProxyProps = ClusterSingletonProxy.Props(
+                singletonManagerPath: "/user/event-log-handler-singleton",
+                settings: ClusterSingletonProxySettings.Create(_actorSystem)
+                    .WithRole(siteRole)
+                    .WithSingletonName("event-log-handler"));
+            var eventLogProxy = _actorSystem.ActorOf(eventLogProxyProps, "event-log-handler-proxy");
+
+            siteCommActor.Tell(new RegisterLocalHandler(LocalHandlerType.EventLog, eventLogProxy));
         }
 
         // Parked message handler — bridges Akka to StoreAndForwardService

src/ScadaLink.SiteRuntime/Actors/ScriptExecutionActor.cs

@@ -6,6 +6,7 @@ using ScadaLink.Commons.Interfaces.Services;
 using ScadaLink.Commons.Messages.ScriptExecution;
 using ScadaLink.Commons.Types;
 using ScadaLink.HealthMonitoring;
+using ScadaLink.SiteEventLogging;
 using ScadaLink.SiteRuntime.Scripts;
 
 namespace ScadaLink.SiteRuntime.Actors;
@@ -71,6 +72,9 @@ public class ScriptExecutionActor : ReceiveActor
         _ = Task.Run(async () =>
         {
             IServiceScope? serviceScope = null;
+            // ISiteEventLogger is a singleton; resolve from the root provider so
+            // it is available to the catch blocks regardless of scope state.
+            var siteEventLogger = serviceProvider?.GetService<ISiteEventLogger>();
             using var cts = new CancellationTokenSource(timeout);
             try
             {
@@ -125,6 +129,10 @@ public class ScriptExecutionActor : ReceiveActor
                 var errorMsg = $"Script '{scriptName}' on instance '{instanceName}' timed out after {timeout.TotalSeconds}s";
                 logger.LogWarning(errorMsg);
 
+                // WP-32: Failures recorded to site event log; script NOT disabled after failure.
+                _ = siteEventLogger?.LogEventAsync(
+                    "script", "Error", instanceName, $"ScriptActor:{scriptName}", errorMsg);
+
                 if (!replyTo.IsNobody())
                 {
                     replyTo.Tell(new ScriptCallResult(correlationId, false, null, errorMsg));
@@ -135,10 +143,13 @@ public class ScriptExecutionActor : ReceiveActor
             catch (Exception ex)
             {
                 healthCollector?.IncrementScriptError();
-                // WP-32: Failures logged to site event log; script NOT disabled after failure
+                // WP-32: Failures recorded to site event log; script NOT disabled after failure.
                 var errorMsg = $"Script '{scriptName}' on instance '{instanceName}' failed: {ex.Message}";
                 logger.LogError(ex, "Script execution failed: {Script} on {Instance}", scriptName, instanceName);
 
+                _ = siteEventLogger?.LogEventAsync(
+                    "script", "Error", instanceName, $"ScriptActor:{scriptName}", errorMsg, ex.ToString());
+
                 if (!replyTo.IsNobody())
                 {
                     replyTo.Tell(new ScriptCallResult(correlationId, false, null, errorMsg));

src/ScadaLink.SiteRuntime/ScadaLink.SiteRuntime.csproj

@@ -24,6 +24,7 @@
     <ProjectReference Include="../ScadaLink.Commons/ScadaLink.Commons.csproj" />
     <ProjectReference Include="../ScadaLink.Communication/ScadaLink.Communication.csproj" />
     <ProjectReference Include="../ScadaLink.HealthMonitoring/ScadaLink.HealthMonitoring.csproj" />
+    <ProjectReference Include="../ScadaLink.SiteEventLogging/ScadaLink.SiteEventLogging.csproj" />
     <ProjectReference Include="../ScadaLink.StoreAndForward/ScadaLink.StoreAndForward.csproj" />
   </ItemGroup>