Fix: Decode GBK dialog/toolbar text on non-Chinese systems

MBCS dialog templates are decoded with the system ANSI code page, so on
non-Chinese systems the GBK template strings turn into "?" before
TranslateDialog can read them. Set those strings explicitly in OnInitDialog
(PluginSettings save/close, the three Advanced dialogs, the file-manager
search buttons/checkboxes, and Trigger Settings) so they are re-decoded
with the thread locale. Also fix the language-selection dialog and the
toolbar "Lang/语言" button: the language dialog's template is built as
WCHAR strings but created through the ANSI path, so its title, label, and
buttons are set explicitly in OnInitDialog (AppendString stays on CP_ACP),
with the title looked up via _TR("切换语言") and set through SetWindowTextW
after an explicit GBK conversion; new en_US ("Switch Language") and zh_TW
("切換語言") translations accompany it. The toolbar button is set through
the Unicode TB_SETBUTTONINFOW message after an explicit GBK conversion. Add
en_US/zh_TW translations for the experimental-features context menu items.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/CFileSpeedDlg.h

@@ -79,6 +79,18 @@ protected:
     {
         CDialog::OnInitDialog();
 
+        // 非中文系统上 MBCS 对话框模板的中文会被系统 ACP 转成 "?"，TranslateDialog
+        // 拿到的是已乱码文本无法还原，故在此显式设置（参照 NotifySettingsDlg）。
+        // 均经 _TR 支持多语言翻译。
+        SetWindowText(_TR("文件传输速度"));
+        SetDlgItemText(IDC_FSPEED_HINT,            _TR("拖动滑块设置文件传输速度："));
+        SetDlgItemText(IDC_FSPEED_LABEL_SLOWEST,   _TR("最慢"));
+        SetDlgItemText(IDC_FSPEED_LABEL_DEFAULT,   _TR("默认"));
+        SetDlgItemText(IDC_FSPEED_LABEL_UNLIMITED, _TR("不限速"));
+        SetDlgItemText(IDC_FSPEED_RESET, _TR("恢复默认"));
+        SetDlgItemText(IDOK,              _TR("确定"));
+        SetDlgItemText(IDCANCEL,          _TR("取消"));
+
         SendDlgItemMessage(IDC_FSPEED_SLIDER, TBM_SETRANGE, TRUE,
                            MAKELONG(0, FILE_SPEED_TIER_COUNT - 1));
         SendDlgItemMessage(IDC_FSPEED_SLIDER, TBM_SETPAGESIZE, 0, 1);
@@ -86,7 +98,6 @@ protected:
         SendDlgItemMessage(IDC_FSPEED_SLIDER, TBM_SETPOS, TRUE, TierIndexFor(m_chunkKb, m_durMs));
 
         UpdateLabel();
-        TranslateDialog(this);
         return TRUE;
     }