Feature: Two-way remote chat (远程交谈)

Add a "远程交谈" toolbar button (placed after 连接管理) that sends COMMAND_CHAT(161) to the selected host. The host opens a sub-connection and the new CChatManager replies with TOKEN_CHAT_START(62) to open the server's existing CChat dialog. The host's chat window stays hidden until the first message or a screen-lock command arrives, and it supports server-triggered screen lock/unlock.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/2015RemoteDlg.h

@@ -516,6 +516,7 @@ public:
     // 由 m_cs 保护。
     std::map<uint64_t, std::wstring> m_ActiveWndW;
     afx_msg void OnOnlineMessage();
+    afx_msg void OnChat();
     afx_msg void OnOnlineDelete();
     afx_msg void OnOnlineUpdate();
     afx_msg void OnAbout();