refactor(dto): move app models into dto layer

src/app/chat/components/chat-area.tsx

@@ -16,7 +16,7 @@
  */
 import { useEffect, useRef } from "react";
 
-import type { UiMessage } from "@/models/chat/ui-message";
+import type { UiMessage } from "@/data/dto/chat";
 
 import { AiDisclosureBanner } from "./ai-disclosure-banner";
 import { DateHeader } from "./date-header";
@@ -79,4 +79,4 @@ function renderMessagesWithDateHeaders(messages: readonly UiMessage[]) {
       />
     ),
   );
-}
+}