feat(commons): native-typed JSON for List values; Decode reads both forms

src/ZB.MOM.WW.ScadaBridge.Commons/Types/AttributeValueCodec.cs

@@ -25,11 +25,10 @@ public static class AttributeValueCodec
             case string s: return s;                       // already canonical
             case IFormattable f: return f.ToString(null, CultureInfo.InvariantCulture);
             case IEnumerable e:
-                var items = e.Cast<object?>()
-                             .Select(x => x is IFormattable xf
-                                 ? xf.ToString(null, CultureInfo.InvariantCulture)
-                                 : x?.ToString());
-                return JsonSerializer.Serialize(items, JsonOpts);
+                // Native-typed JSON: serialize the runtime collection so System.Text.Json emits
+                // numbers/bools unquoted, strings quoted, and DateTime as ISO-8601. Boxed as object
+                // so STJ uses the runtime element type. STJ numbers/dates are culture-invariant.
+                return JsonSerializer.Serialize<object>(e, JsonOpts);
             default: return value.ToString();
         }
     }
@@ -46,18 +45,25 @@ public static class AttributeValueCodec
         if (elementType is null)
             throw new FormatException("List attribute requires an element type.");
 
-        string?[] raw;
-        try { raw = JsonSerializer.Deserialize<string?[]>(value) ?? []; }
+        JsonElement[] raw;
+        try { raw = JsonSerializer.Deserialize<JsonElement[]>(value) ?? []; }
         catch (JsonException ex) { throw new FormatException("Malformed list JSON.", ex); }
 
         var clrType = ElementClrType(elementType.Value);
         var listType = typeof(List<>).MakeGenericType(clrType);
         var result = (IList)Activator.CreateInstance(listType)!;
-        foreach (var item in raw)
-            result.Add(ParseScalar(item, elementType.Value));
+        foreach (var el in raw)
+            result.Add(ParseScalar(JsonElementToString(el), elementType.Value));
         return result;
     }
 
+    private static string? JsonElementToString(JsonElement el) => el.ValueKind switch
+    {
+        JsonValueKind.String => el.GetString(),   // old form, or string-typed lists
+        JsonValueKind.Null => null,               // ParseScalar throws "may not be null"
+        _ => el.GetRawText()                       // number/bool → "10" / "1.5" / "true"
+    };
+
     private static Type ElementClrType(DataType t) => t switch
     {
         DataType.String => typeof(string),