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/ScriptExecutionActor.cs

@@ -47,6 +47,7 @@ public class ScriptExecutionActor : ReceiveActor
     /// <param name="healthCollector">Optional health collector for recording execution metrics.</param>
     /// <param name="serviceProvider">Optional DI service provider for script execution services.</param>
     /// <param name="parentExecutionId">ExecutionId of the spawning inbound-API execution for audit correlation; null for normal runs.</param>
+    /// <param name="executionTimeoutSeconds">M2.5 (#9): per-script execution timeout in seconds. Null or non-positive falls back to the global <see cref="SiteRuntimeOptions.ScriptExecutionTimeoutSeconds"/>.</param>
     public ScriptExecutionActor(
         string scriptName,
         string instanceName,
@@ -65,7 +66,10 @@ public class ScriptExecutionActor : ReceiveActor
         // Audit Log #23 (ParentExecutionId): the spawning execution's
         // ExecutionId for an inbound-API-routed call. Null for normal
         // (tag-change / timer) runs and nested Script.Call invocations.
-        Guid? parentExecutionId = null)
+        Guid? parentExecutionId = null,
+        // M2.5 (#9): per-script execution timeout override (seconds). Null or
+        // non-positive falls back to the global ScriptExecutionTimeoutSeconds.
+        int? executionTimeoutSeconds = null)
     {
         // Immediately begin execution
         var self = Self;
@@ -75,7 +79,7 @@ public class ScriptExecutionActor : ReceiveActor
             scriptName, instanceName, compiledScript, parameters, callDepth,
             instanceActor, sharedScriptLibrary, options, replyTo, correlationId,
             self, parent, logger, scope, healthCollector, serviceProvider,
-            parentExecutionId);
+            parentExecutionId, executionTimeoutSeconds);
     }
 
     private static void ExecuteScript(
@@ -95,9 +99,15 @@ public class ScriptExecutionActor : ReceiveActor
         Commons.Types.Scripts.ScriptScope scope,
         ISiteHealthCollector? healthCollector,
         IServiceProvider? serviceProvider,
-        Guid? parentExecutionId)
+        Guid? parentExecutionId,
+        int? executionTimeoutSeconds)
     {
-        var timeout = TimeSpan.FromSeconds(options.ScriptExecutionTimeoutSeconds);
+        // M2.5 (#9): per-script timeout overrides the global default. A null or
+        // non-positive per-script value (≤ 0) falls back to the global.
+        var timeout = TimeSpan.FromSeconds(
+            executionTimeoutSeconds is { } perScript && perScript > 0
+                ? perScript
+                : options.ScriptExecutionTimeoutSeconds);
 
         // SiteRuntime-009: run the script body on the dedicated script-execution
         // scheduler, not the shared .NET thread pool, so blocking script I/O cannot