fix(commons): LoadLegacy handles mixed-type JSON values (number/bool/string)

tests/ScadaLink.Commons.Tests/Types/DataConnections/OpcUaEndpointConfigSerializerTests.cs

@@ -114,6 +114,27 @@ public class OpcUaEndpointConfigSerializerTests
         Assert.Equal("opc.tcp://x:4840", config.EndpointUrl);
     }
 
+    [Fact]
+    public void Deserialize_LegacyWithMixedTypeValues_PreservesAllFields()
+    {
+        // Real-world legacy producer emitted mixed JSON value types:
+        // string for endpoint, number for publishInterval, etc.
+        var legacyJson = """
+            {"endpoint":"opc.tcp://scadalink-opcua:50000","securityMode":"None","publishInterval":1000,"AutoAcceptUntrustedCerts":false,"SessionTimeoutMs":45000}
+            """;
+
+        var (config, isLegacy) = OpcUaEndpointConfigSerializer.Deserialize(legacyJson);
+
+        Assert.True(isLegacy);
+        Assert.Equal("opc.tcp://scadalink-opcua:50000", config.EndpointUrl);
+        Assert.Equal(OpcUaSecurityMode.None, config.SecurityMode);
+        Assert.False(config.AutoAcceptUntrustedCerts);
+        Assert.Equal(45000, config.SessionTimeoutMs);
+        // publishInterval is not a recognized key (the real key is PublishingIntervalMs);
+        // FromFlatDict ignores unknown keys, so PublishingIntervalMs stays at its POCO default of 1000.
+        Assert.Equal(1000, config.PublishingIntervalMs);
+    }
+
     [Theory]
     [InlineData("not json at all")]
     [InlineData("[1,2,3]")]