Feature: Add exec_command MCP tool

Add a one-shot exec_command MCP tool that runs a command on a remote
Windows host and returns stdout plus exit code, reusing the Web terminal
link (main-connection COMMAND_SHELL, a shell sub-connection, and a
sentinel command line located via rfind to tolerate ConPTY echo).

The sentinel marker is embedded in the command line ConPTY echoes back,
so it is only treated as hit when it starts a line (preceded by a newline
or the buffer start); this keeps the echoed marker from being mistaken
for the real sentinel when the echo packet arrives before the output.

Execution is gated at Web remote-desktop sensitivity: a read-only mode
(McpReadonly, default on, hides the tool) and a command whitelist
(McpCmdWhitelist) with built-in read-only prefixes. Shell metacharacters
(& | < > ^) are rejected before whitelist matching, and each execution is
recorded in the server audit log.

Extend the MCP settings dialog with the read-only checkbox and a
multi-line whitelist box (commas and newlines both accepted, normalized
to a comma-separated list on save), and add English and Traditional
Chinese mappings for the new UI and audit-log strings.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/McpSettingsDlg.h

@@ -26,11 +26,16 @@ private:
         IDC_MCP_PORT   = 1002,  // 端口编辑框
         IDC_MCP_BIND   = 1003,  // 绑定地址编辑框
         IDC_MCP_TOKEN  = 1004,  // Token 编辑框
+        IDC_MCP_READONLY  = 1005,  // 「只读模式」复选框（默认勾选，禁 exec_command）
+        IDC_MCP_WHITELIST = 1006,  // 命令白名单编辑框（多行，逗号/换行分隔，空 = 内置只读前缀）
     };
 
     CButton m_btnEnable;
     CStatic m_lblPort, m_lblBind, m_lblToken;
     CEdit   m_editPort, m_editBind, m_editToken;
+    CButton m_btnReadonly;
+    CStatic m_lblWhitelist;
+    CEdit   m_editWhitelist;
     CButton m_btnOK, m_btnCancel;
 
     std::vector<BYTE> m_Template;  // 内存 DLGTEMPLATE 字节