chore: use file-scoped namespace

src/Shared/HandyControlDemo_Shared/Data/Model/CardModel.cs

@@ -1,11 +1,10 @@
-namespace HandyControlDemo.Data
+namespace HandyControlDemo.Data;
+
+public class CardModel
 {
-    public class CardModel
-    {
-        public string Header { get; set; }
+    public string Header { get; set; }
 
-        public string Content { get; set; }
+    public string Content { get; set; }
 
-        public string Footer { get; set; }
-    }
-}
+    public string Footer { get; set; }
+}