feat(weChat): 添加联系人存在检查逻辑并优化消息处理

在setCurrentContact方法中添加isExist参数，用于区分新增联系人和已存在联系人的处理逻辑
优化消息处理流程，确保未读消息计数正确更新

Cunkebao/src/pages/pc/ckbox/components/SidebarMenu/MessageList/index.tsx

@@ -13,7 +13,7 @@ const MessageList: React.FC<MessageListProps> = () => {
   const { setCurrentContact, currentContract } = useWeChatStore();
   const chatSessions = useCkChatStore(state => state.chatSessions);
   const onContactClick = (session: ContractData | weChatGroup) => {
-    setCurrentContact(session);
+    setCurrentContact(session, true);
   };
   return (
     <div className={styles.messageList}>