feat(commons): add DataSourceReferenceOverride to InstanceConnectionBinding

src/ZB.MOM.WW.ScadaBridge.Commons/Entities/Instances/InstanceConnectionBinding.cs

@@ -11,6 +11,14 @@ public class InstanceConnectionBinding
     /// <summary>Foreign key to the data connection that provides values for this attribute.</summary>
     public int DataConnectionId { get; set; }
 
+    /// <summary>
+    /// Optional per-instance override of the OPC UA node identifier (or other
+    /// protocol address) for this attribute. When non-null, this value replaces
+    /// the template's <c>DataSourceReference</c> during flattening. When null,
+    /// the template default is used.
+    /// </summary>
+    public string? DataSourceReferenceOverride { get; set; }
+
     /// <summary>
     /// Creates a binding for the specified attribute name.
     /// </summary>