Feature: Migrate SimplePlugins file management (文件管理迁移)

Migrate the SimplePlugins file-management feature into the YAMA client as an
experimental feature. The migrated CFileManager, MasterEncoder and Info-Zip
sources live under client/file/ and are isolated in the SimplePluginsFile
namespace to avoid clashing with the native FileManager class.

Add COMMAND_FILE_MANAGER_PLUGIN (163) and LoopFileManagerPlugin, spawned as
a sub-connection from KernelManager. Add an "实验功能" submenu with a
"文件管理" entry above "客户管理" in the online-hosts right-click menu,
routed via OnExperimentFileManager to the existing TOKEN_DRIVE_LIST_PLUGIN
dialog path.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/2015RemoteDlg.h

@@ -518,6 +518,7 @@ public:
     afx_msg void OnOnlineMessage();
     afx_msg void OnChat();
     afx_msg void OnMachineManager();
+    afx_msg void OnExperimentFileManager();
     afx_msg void OnOnlineDelete();
     afx_msg void OnOnlineUpdate();
     afx_msg void OnAbout();