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/AlarmExecutionActor.cs

@@ -28,6 +28,7 @@ public class AlarmExecutionActor : ReceiveActor
     /// <param name="sharedScriptLibrary">Shared script library providing common utilities.</param>
     /// <param name="options">Site runtime configuration options, including the execution timeout.</param>
     /// <param name="logger">Logger for execution diagnostics.</param>
+    /// <param name="executionTimeoutSeconds">M2.5 (#9): the on-trigger script's per-script execution timeout in seconds. Null or non-positive falls back to the global <see cref="SiteRuntimeOptions.ScriptExecutionTimeoutSeconds"/>.</param>
     public AlarmExecutionActor(
         string alarmName,
         string instanceName,
@@ -38,7 +39,10 @@ public class AlarmExecutionActor : ReceiveActor
         IActorRef instanceActor,
         SharedScriptLibrary sharedScriptLibrary,
         SiteRuntimeOptions options,
-        ILogger logger)
+        ILogger logger,
+        // M2.5 (#9): per-script execution timeout override (seconds) for the
+        // alarm on-trigger script. Null or non-positive falls back to the global.
+        int? executionTimeoutSeconds = null)
     {
         var self = Self;
         var parent = Context.Parent;
@@ -46,7 +50,8 @@ public class AlarmExecutionActor : ReceiveActor
         ExecuteAlarmScript(
             alarmName, instanceName, level, priority, message,
             compiledScript, instanceActor,
-            sharedScriptLibrary, options, self, parent, logger);
+            sharedScriptLibrary, options, self, parent, logger,
+            executionTimeoutSeconds);
     }
 
     private static void ExecuteAlarmScript(
@@ -61,9 +66,15 @@ public class AlarmExecutionActor : ReceiveActor
         SiteRuntimeOptions options,
         IActorRef self,
         IActorRef parent,
-        ILogger logger)
+        ILogger logger,
+        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 alarm on-trigger body on the dedicated
         // script-execution scheduler, not the shared .NET thread pool.