feat(runtime): per-script execution timeout overriding the global default (#9)

Spec promised a per-script timeout but only the global ScriptExecutionTimeoutSeconds
existed. Add nullable TemplateScript.ExecutionTimeoutSeconds threaded through EF +
flattening (ResolvedScript) to ScriptExecutionActor/AlarmExecutionActor, which use
perScript ?? global for the execution CTS. Includes the EF migration for the new column.

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Actors/ScriptActor.cs

@@ -43,6 +43,13 @@ public class ScriptActor : ReceiveActor, IWithTimers
     private Script<object?>? _compiledScript;
     private ScriptTriggerConfig? _triggerConfig;
     private TimeSpan? _minTimeBetweenRuns;
+
+    /// <summary>
+    /// M2.5 (#9): the per-script execution timeout in seconds, or null to use the
+    /// global default. Threaded down to each spawned <see cref="ScriptExecutionActor"/>,
+    /// which applies <c>perScript ?? global</c> (and treats ≤ 0 as "use global").
+    /// </summary>
+    private readonly int? _executionTimeoutSeconds;
     private DateTimeOffset _lastExecutionTime = DateTimeOffset.MinValue;
     private int _executionCounter;
     private readonly Commons.Types.Scripts.ScriptScope _scope;
@@ -112,6 +119,7 @@ public class ScriptActor : ReceiveActor, IWithTimers
         _healthCollector = healthCollector;
         _serviceProvider = serviceProvider;
         _minTimeBetweenRuns = scriptConfig.MinTimeBetweenRuns;
+        _executionTimeoutSeconds = scriptConfig.ExecutionTimeoutSeconds;
         _scope = scriptConfig.Scope;
         _compiledTriggerExpression = compiledTriggerExpression;
 
@@ -426,7 +434,9 @@ public class ScriptActor : ReceiveActor, IWithTimers
             _serviceProvider,
             // Audit Log #23 (ParentExecutionId): null for trigger-driven runs;
             // an inbound-API-routed call supplies the inbound request's id.
-            parentExecutionId));
+            parentExecutionId,
+            // M2.5 (#9): per-script timeout override (null = use global).
+            _executionTimeoutSeconds));
 
         Context.ActorOf(props, executionId);
     }