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/context.h

@@ -55,6 +55,16 @@ public:
     }
     virtual void SetGroupName(const std::string& group) {}
 
+    // 等待本连接待发送缓冲排空（用于「发写命令 → 补发刷新命令」的背靠背发送：
+    // 两次 Send2Client 会对同一发送缓冲并发 WSASend，造成竞态/丢包）。非 IOCP
+    // 服务端无异步发送缓冲，默认立即返回 true；CONTEXT_OBJECT 覆写为轮询发送缓冲
+    // 归零直到排空或超时。
+    virtual bool WaitSendIdle(int timeoutMs)
+    {
+        (void)timeoutMs;
+        return true;
+    }
+
     // 检查客户端是否支持 V2 文件传输
     bool SupportsFileV2() const {
         CString caps = GetClientData(ONLINELIST_CAPABILITIES);