Feature: Add file-transfer speed dialog with multi-language support

Add a novice-friendly "File Transfer Speed" dialog under the Advanced menu
that controls file-transfer speed in both directions without touching
SimplePlugins. Speed is passed through InitFileUpload's existing
chunkSizeKb/sendDurationMs arguments, so the precompiled library stays
untouched. Seven presets run from ~0.3 MB/s up to a new 10 MB/s tier plus an
unlimited tier; the chosen value is stored in [transfer] ChunkKb/DurationMs.

Upload reads THIS_CFG at the master's InitFileUpload (2015RemoteDlg.cpp:2225)
and takes effect on restart. Download is pushed to the client over a new
CMD_FILE_SPEED (252) command, sent from OnOnlineFileManager and
OnOnlineDesktopManager before each session opens, and read by all four client
InitFileUpload call sites via GetTransferSpeed so the process-global refcount
cannot latch a stale speed. All Chinese strings go through LangManager, with
en_US/zh_TW/de_DE entries added for the tier names, format strings and hint
text.

Co-Authored-By: deepseek-v4-pro

client/FileManager.cpp

@@ -36,9 +36,13 @@ CFileManager::CFileManager(CClientSocket *pClient, int h, void* user):CManager(p
     // 初始化V2文件传输模块
     CKernelManager* main = (CKernelManager*)pClient->GetMain();
     m_Signature = main ? main->m_LoginSignature : pClient->m_LoginSignature;
-    if (!m_Signature.empty())
+    if (!m_Signature.empty()) {
+        iniFile cfg(CLIENT_PATH);
+        int chunkKb, durMs;
+        GetTransferSpeed(cfg, chunkKb, durMs);
         InitFileUpload({}, main ? main->m_LoginMsg : pClient->m_LoginMsg,
-        main ? main->m_LoginSignature : pClient->m_LoginSignature, 64, 50, Logf);
+        main ? main->m_LoginSignature : pClient->m_LoginSignature, chunkKb, durMs, Logf);
+    }
 
     // 发送驱动器列表, 开始进行文件管理，建立新线程
     SendDriveList();