refactor: rename DTree to DValue

site/examples/uce-starter/views/auth/demo.uce

@@ -2,12 +2,12 @@
 
 COMPONENT(Request& context)
 {
-	DTree asset_props;
+	DValue asset_props;
 	asset_props["css"]["0"] = "views/marketing.css";
 	print(component("../../components/theme/assets", asset_props, context));
 	context.call["app"]["page_title"] = "Auth";
 
-	DTree props;
+	DValue props;
 	props["title"] = "Sign In to Your Account";
 	props["subtitle"] = "Choose your preferred authentication method to continue";
 	props["google_client_id"] = "YOUR_GOOGLE_CLIENT_ID";