feat(esg): per-system TimeoutSeconds column on ExternalSystemDefinition (spec Component-ExternalSystemGateway Timeout) — entity + EF + migration

Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj

tests/ZB.MOM.WW.ScadaBridge.Commons.Tests/Entities/ExternalSystemDefinitionTests.cs

@@ -0,0 +1,19 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Entities.ExternalSystems;
+
+namespace ZB.MOM.WW.ScadaBridge.Commons.Tests.Entities;
+
+/// <summary>
+/// Locks the <see cref="ExternalSystemDefinition"/> construction invariants — in particular
+/// that the per-system <see cref="ExternalSystemDefinition.TimeoutSeconds"/> defaults to 0,
+/// meaning "unset — use the gateway's configured DefaultHttpTimeout".
+/// </summary>
+public class ExternalSystemDefinitionTests
+{
+    [Fact]
+    public void ExternalSystemDefinition_TimeoutSeconds_DefaultsToZeroMeaningUseGatewayDefault()
+    {
+        var system = new ExternalSystemDefinition("sys", "http://x", "none");
+
+        Assert.Equal(0, system.TimeoutSeconds);
+    }
+}

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

@@ -45,6 +45,21 @@ public class ExternalSystemRepositoryTests : IDisposable
         Assert.Equal("Sys", loaded!.Name);
     }
 
+    [Fact]
+    public async Task AddExternalSystem_TimeoutSeconds_RoundTrips()
+    {
+        var def = new ExternalSystemDefinition("Sys", "https://example.test", "ApiKey")
+        {
+            TimeoutSeconds = 15,
+        };
+        await _repository.AddExternalSystemAsync(def);
+        await _repository.SaveChangesAsync();
+
+        var loaded = await _repository.GetExternalSystemByIdAsync(def.Id);
+        Assert.NotNull(loaded);
+        Assert.Equal(15, loaded!.TimeoutSeconds);
+    }
+
     [Fact]
     public async Task GetMethodsByExternalSystemId_FiltersByParent()
     {