feat: 이미 읽은 메시지를 DB에서 처리

hwe/ts/defs/API/Message.ts

@@ -58,6 +58,10 @@ export type MsgResponse = {
   nationID: number;
   generalName: string;
   sequence: number;
+  latestRead?: {
+    private: number;
+    diplomacy: number;
+  }
 };
 
 export type MailboxItem = {