add Platform property to SiteState and populate on both Web and .NET MAUI

Oqtane.Shared/Shared/SiteState.cs

@@ -12,6 +12,7 @@ namespace Oqtane.Shared
         public string AntiForgeryToken { get; set; } // passed from server for use in service calls on client
         public string AuthorizationToken { get; set; } // passed from server for use in service calls on client
         public string RemoteIPAddress { get; set; } // passed from server as cannot be reliably retrieved on client
+        public string Platform { get; set; }
         public bool IsPrerendering { get; set; }
 
         private dynamic _properties;