Feature: Add MCP (Model Context Protocol) server integration

Add an optional MCP server (JSON-RPC 2.0 over Streamable HTTP) exposing
an online-host listing tool, protected by a Bearer token. Disabled by
default; configured via a new "Extensions > MCP Settings" dialog.

- McpServer: httplib + JSON-RPC 2.0 dispatch (initialize/ping/tools/list/tools/call)
- McpSettingsDlg: runtime-created dialog for enable/port/bind/token
- HostJson: extract single-host JSON serialization shared with WebService
- FRP: expose MCP port (union with listening/Web ports) when bound to 0.0.0.0
- i18n: en_US / zh_TW translations

Co-Authored-By: deepseek-v4-pro

server/2015Remote/2015RemoteDlg.h

@@ -638,6 +638,7 @@ public:
     afx_msg void OnMasterTrail();
     afx_msg void OnCancelShare();
     afx_msg void OnWebRemoteControl();
+    afx_msg void OnMcpSettings();
     afx_msg void OnProxyPortAutorun();
     afx_msg void OnScreenpreviewLoop();
     afx_msg void OnMenuCompress();