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

server/2015Remote/CFileSpeedDlg.h

@@ -0,0 +1,122 @@
+// CFileSpeedDlg.h
+// 文件传输速度调节对话框：拖动滑块选档位，实时显示预估速度。
+// 纯主控端 UI 偏好，持久化由 CMy2015RemoteDlg::OnFileTransferSpeed() 负责。
+// 仅在 2015RemoteDlg.cpp 中 include 一次（头文件内联实现 + 消息映射，勿多处包含）。
+#pragma once
+
+#include "LangManager.h"
+#include <afxcmn.h>
+
+// 档位表（权威来源：docs/FileTransferSpeed_Design.md §3）。
+// chunkKb * 1024 / durationMs 即理论字节/秒；durationMs==0 表示不人为限速。
+struct FileSpeedTier { int chunkKb; int durMs; const TCHAR* name; };
+
+static const FileSpeedTier kFileSpeedTiers[] = {
+    {   64, 200, _T("最慢")   },   // ≈0.31 MB/s
+    {   64, 100, _T("慢")     },   // ≈0.63 MB/s
+    {   64,  50, _T("默认")   },   // ≈1.25 MB/s
+    {  128,  50, _T("快")     },   // ≈2.5  MB/s
+    {  256,  50, _T("更快")   },   // ≈5    MB/s
+    {  512,  50, _T("很快")   },   // ≈10   MB/s
+    { 1024,   0, _T("不限速") },   // 网络上限
+};
+#define FILE_SPEED_TIER_COUNT 7
+#define FILE_SPEED_DEFAULT_TIER 2   // 默认档位
+
+class CFileSpeedDlg : public CDialog
+{
+public:
+    enum { IDD = IDD_FILE_SPEED };
+
+    CFileSpeedDlg(int chunkKb, int durMs, CWnd* pParent = NULL)
+        : CDialog(CFileSpeedDlg::IDD, pParent), m_chunkKb(chunkKb), m_durMs(durMs)
+    {
+    }
+
+    int GetChunkKb() const { return m_chunkKb; }
+    int GetDurMs()   const { return m_durMs; }
+
+protected:
+    int m_chunkKb;
+    int m_durMs;
+
+    static int TierIndexFor(int chunkKb, int durMs)
+    {
+        for (int i = 0; i < FILE_SPEED_TIER_COUNT; i++)
+            if (kFileSpeedTiers[i].chunkKb == chunkKb && kFileSpeedTiers[i].durMs == durMs)
+                return i;
+        return FILE_SPEED_DEFAULT_TIER;   // 未知值回落默认
+    }
+
+    static void FormatSpeed(int idx, CString& out)
+    {
+        const FileSpeedTier& t = kFileSpeedTiers[idx];
+        // 档位名与格式串经 _TR/_LF 走多语言表（LangManager），语言文件以中文原文为 key。
+        if (t.durMs <= 0) {
+            out.FormatL(_T("%s · 不受限速（受网络带宽约束）"), _LF(t.name));
+            return;
+        }
+        double mbps = (double)t.chunkKb * 1024.0 / (t.durMs / 1000.0) / (1024.0 * 1024.0);
+        out.FormatL(_T("%s · 约 %.2f MB/s"), _LF(t.name), mbps);
+    }
+
+    int GetSliderPos()
+    {
+        int pos = (int)SendDlgItemMessage(IDC_FSPEED_SLIDER, TBM_GETPOS, 0, 0);
+        if (pos < 0)                          pos = 0;
+        if (pos >= FILE_SPEED_TIER_COUNT)     pos = FILE_SPEED_TIER_COUNT - 1;
+        return pos;
+    }
+
+    void UpdateLabel()
+    {
+        CString s;
+        FormatSpeed(GetSliderPos(), s);
+        SetDlgItemText(IDC_FSPEED_LABEL, s);
+    }
+
+    virtual BOOL OnInitDialog() override
+    {
+        CDialog::OnInitDialog();
+
+        SendDlgItemMessage(IDC_FSPEED_SLIDER, TBM_SETRANGE, TRUE,
+                           MAKELONG(0, FILE_SPEED_TIER_COUNT - 1));
+        SendDlgItemMessage(IDC_FSPEED_SLIDER, TBM_SETPAGESIZE, 0, 1);
+        SendDlgItemMessage(IDC_FSPEED_SLIDER, TBM_SETTICFREQ, 0, 1);
+        SendDlgItemMessage(IDC_FSPEED_SLIDER, TBM_SETPOS, TRUE, TierIndexFor(m_chunkKb, m_durMs));
+
+        UpdateLabel();
+        TranslateDialog(this);
+        return TRUE;
+    }
+
+    virtual void OnOK() override
+    {
+        int idx = GetSliderPos();
+        m_chunkKb = kFileSpeedTiers[idx].chunkKb;
+        m_durMs   = kFileSpeedTiers[idx].durMs;
+        CDialog::OnOK();
+    }
+
+    afx_msg void OnHScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
+    {
+        (void)nSBCode; (void)nPos; (void)pScrollBar;
+        UpdateLabel();   // 拖动过程中实时刷新预估速度
+    }
+
+    virtual BOOL OnCommand(WPARAM wParam, LPARAM lParam) override
+    {
+        if (LOWORD(wParam) == IDC_FSPEED_RESET && HIWORD(wParam) == BN_CLICKED) {
+            SendDlgItemMessage(IDC_FSPEED_SLIDER, TBM_SETPOS, TRUE, FILE_SPEED_DEFAULT_TIER);
+            UpdateLabel();
+            return TRUE;
+        }
+        return CDialog::OnCommand(wParam, lParam);
+    }
+
+    DECLARE_MESSAGE_MAP()
+};
+
+BEGIN_MESSAGE_MAP(CFileSpeedDlg, CDialog)
+    ON_WM_HSCROLL()
+END_MESSAGE_MAP()