feat(siteeventlog): emit script started/completed Info events (M1.8)

ScriptExecutionActor previously emitted only an Error 'script' event on failure.
It now also fire-and-forgets an Info 'script' event when execution starts (right
before RunAsync) and when it completes successfully — giving the operational log
the full started/completed/failed lifecycle. Uses the already-resolved
siteEventLogger; fire-and-forget so the event log can never block or fault the
script's own run.

Extends the SingleServiceProvider test helper to also serve IServiceScopeFactory
(returning a self-scope) so ScriptExecutionActor's serviceProvider.CreateScope()
reaches the logging hot path in tests instead of throwing into the catch.

tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/TestSupport/FakeSiteEventLogger.cs

@@ -1,4 +1,5 @@
 using System.Collections.Concurrent;
+using Microsoft.Extensions.DependencyInjection;
 using ZB.MOM.WW.ScadaBridge.SiteEventLogging;
 
 namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests.TestSupport;
@@ -51,12 +52,32 @@ public sealed class FakeSiteEventLogger : ISiteEventLogger
 /// <see cref="ISiteEventLogger"/> — enough for the actors' optional
 /// <c>_serviceProvider?.GetService&lt;ISiteEventLogger&gt;()</c> resolution
 /// without pulling a full DI container into the actor tests.
+/// <para>
+/// Also serves <see cref="IServiceScopeFactory"/> (returning a scope that just
+/// re-exposes this provider) so callers that do
+/// <c>serviceProvider.CreateScope()</c> — e.g. <c>ScriptExecutionActor</c> —
+/// don't throw before they reach the logging hot path.
+/// </para>
 /// </summary>
-public sealed class SingleServiceProvider(ISiteEventLogger logger) : IServiceProvider
+public sealed class SingleServiceProvider(ISiteEventLogger logger)
+    : IServiceProvider, IServiceScopeFactory, IServiceScope
 {
     private readonly ISiteEventLogger _logger = logger;
 
     /// <inheritdoc />
-    public object? GetService(Type serviceType) =>
-        serviceType == typeof(ISiteEventLogger) ? _logger : null;
+    public object? GetService(Type serviceType)
+    {
+        if (serviceType == typeof(ISiteEventLogger)) return _logger;
+        if (serviceType == typeof(IServiceScopeFactory)) return this;
+        return null;
+    }
+
+    /// <inheritdoc />
+    public IServiceScope CreateScope() => this;
+
+    /// <inheritdoc />
+    public IServiceProvider ServiceProvider => this;
+
+    /// <inheritdoc />
+    public void Dispose() { }
 }