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.

tests/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests/TemplateEngineRepositoryTests.cs

@@ -61,6 +61,34 @@ public class TemplateEngineRepositoryTests : IDisposable
         Assert.Equal("Slot1", loaded.Compositions.First().InstanceName);
     }
 
+    [Fact]
+    public async Task TemplateScript_ExecutionTimeoutSeconds_RoundTripsThroughEf()
+    {
+        // M2.5 (#9): the nullable per-script execution timeout must persist and
+        // reload through EF — both an explicit value and a null (use-global).
+        var template = new Template("TimeoutTemplate");
+        template.Scripts.Add(new TemplateScript("WithTimeout", "return 1;")
+        {
+            ExecutionTimeoutSeconds = 45
+        });
+        template.Scripts.Add(new TemplateScript("NoTimeout", "return 2;")); // null
+        _context.Templates.Add(template);
+        await _context.SaveChangesAsync();
+
+        // Detach so the reload comes from the store, not the change tracker.
+        _context.ChangeTracker.Clear();
+
+        var loaded = await _context.Templates
+            .Include(t => t.Scripts)
+            .SingleAsync(t => t.Name == "TimeoutTemplate");
+
+        var withTimeout = loaded.Scripts.Single(s => s.Name == "WithTimeout");
+        Assert.Equal(45, withTimeout.ExecutionTimeoutSeconds);
+
+        var noTimeout = loaded.Scripts.Single(s => s.Name == "NoTimeout");
+        Assert.Null(noTimeout.ExecutionTimeoutSeconds);
+    }
+
     [Fact]
     public async Task GetTemplateWithChildrenAsync_ReturnsNull_WhenTemplateDoesNotExist()
     {