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/lang/zh_TW.ini

@@ -1978,4 +1978,7 @@ MCP
 端口需为 1-65535 的数字=連接埠需為 1-65535 的數字
 Token 不能为空=Token 不能為空
 MCP 设置已保存。=MCP 設定已儲存。
-启用/端口/绑定地址/Token 的改动需重启程序生效。=啟用/連接埠/綁定位址/Token 的變更需重新啟動程式後生效。
+启用/端口/绑定地址/Token/只读/白名单的改动需重启程序生效。=啟用/連接埠/綁定位址/Token/唯讀/白名單的變更需重新啟動程式後生效。
+只读模式（禁命令执行）=唯讀模式（禁命令執行）
+命令白名单=命令白名單
+MCP命令执行=MCP命令執行