fix(mgmt): MV-10 review fixes (ElementDataType fixed-field in LockEnforcer; graceful bad-DataType error; message consistency)

src/ZB.MOM.WW.ScadaBridge.TemplateEngine/LockEnforcer.cs

@@ -15,7 +15,7 @@ namespace ZB.MOM.WW.ScadaBridge.TemplateEngine;
 ///   overrides that were previously blocked (TemplateEngine-022).
 ///
 /// Override granularity:
-/// - Attributes: Value and Description overridable; DataType and DataSourceReference fixed.
+/// - Attributes: Value and Description overridable; DataType, ElementDataType and DataSourceReference fixed.
 /// - Alarms: Priority, TriggerConfiguration, Description, OnTriggerScript overridable; Name and TriggerType fixed.
 /// - Scripts: Code, TriggerConfiguration, MinTimeBetweenRuns, ExecutionTimeoutSeconds, params/return overridable; Name fixed.
 /// - Lock flag applies to the entire member (attribute/alarm/script).
@@ -43,6 +43,12 @@ public static class LockEnforcer
             return $"Attribute '{original.Name}': DataType cannot be overridden (fixed).";
         }
 
+        // ElementDataType is fixed (the element scalar type of a List attribute) — cannot change
+        if (proposed.ElementDataType != original.ElementDataType)
+        {
+            return $"Attribute '{original.Name}': ElementDataType cannot be overridden (fixed).";
+        }
+
         // DataSourceReference is fixed — cannot change
         if (proposed.DataSourceReference != original.DataSourceReference)
         {

src/ZB.MOM.WW.ScadaBridge.TemplateEngine/TemplateService.cs

@@ -982,6 +982,7 @@ public class TemplateService
             {
                 Value = attr.Value,
                 DataType = attr.DataType,
+                ElementDataType = attr.ElementDataType,
                 IsLocked = attr.IsLocked,
                 Description = attr.Description,
                 DataSourceReference = attr.DataSourceReference,