Feature: Add MCP device management-control tools (kill/window/service/power)

Add P7 management-control tools behind a single McpManage flag (plus
McpReadonly=0): kill_process, operate_window, control_service and
power_action. The write tools run a ready->confirm lifecycle on their
sub-connection, using a new followUp/followUpSent field to tell the two
arrivals of the same TOKEN_*LIST apart; the write command and the follow-up
refresh command go out as two separate Send2Client calls, with a new
WaitSendIdle() (context.h / Server.h) draining the outbound buffer in between
so the same buffer is never WSASend'd concurrently.

McpSettingsDlg gains a "management operations" checkbox (IDC_MCP_MANAGE), the
main toolbar gains an MCP entry button, and en/de/zh-TW strings are synced.
power_action is fire-and-forget over the main connection (no confirmation).

Verified end-to-end against a real Windows 10/VMware client: kill_process
returns remaining:[] and operate_window/control_service return ok:true with
their confirm packet arriving after an HTTP split. Verification surfaced a
prerequisite parser bug, fixed separately in a72e6eb, where HeaderParser
latched m_bShouldUnmask FALSE on HTTP continuation chunks and dropped the
confirm packet.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/McpSettingsDlg.h

@@ -31,6 +31,7 @@ private:
         IDC_MCP_TERMINAL  = 1007,  // 「启用持久终端」复选框（全命令，无白名单，要求只读关）
         IDC_MCP_REMOTECONTROL = 1008,  // 「启用远程控制」复选框（AI 操控桌面，要求只读关）
         IDC_MCP_FILETRANSFER = 1009,  // 「启用文件传输」复选框（download_file，不要求只读关）
+        IDC_MCP_MANAGE      = 1010,  // 「启用管理操作」复选框（kill/窗口/服务/电源，要求只读关）
     };
 
     CButton m_btnEnable;
@@ -40,6 +41,7 @@ private:
     CButton m_btnTerminal;
     CButton m_btnRemoteControl;
     CButton m_btnFileTransfer;
+    CButton m_btnManage;
     CStatic m_lblWhitelist;
     CEdit   m_editWhitelist;
     CButton m_btnOK, m_btnCancel;