feat(chat): support ai photo viewing

src/data/dto/chat/chat_message.ts

@@ -12,6 +12,7 @@ export class ChatMessage {
   declare readonly content: string;
   declare readonly id: string;
   declare readonly createdAt: string;
+  declare readonly imageUrl: string | null;
   declare readonly isPrivate: boolean | null;
   declare readonly privateLocked: boolean | null;
   declare readonly privateHint: string | null;