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/QualityLevelsDlg.h

@@ -124,11 +124,31 @@ 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/_L 支持多语言翻译。
+        SetWindowText(_TR("远程桌面质量等级"));
+        SetDlgItemText(IDC_QLEVEL_LABEL_LEVEL,   _TR("等级"));
+        SetDlgItemText(IDC_QLEVEL_LABEL_FPS,     _TR("帧率(FPS)"));
+        SetDlgItemText(IDC_QLEVEL_LABEL_WIDTH,   _TR("最大宽度"));
+        SetDlgItemText(IDC_QLEVEL_LABEL_ALGO,    _TR("编码算法"));
+        SetDlgItemText(IDC_QLEVEL_LABEL_BITRATE, _TR("码率(kbps)"));
+        static const TCHAR* kLevelNames[QUALITY_COUNT] = {
+            _T("Ultra 极佳"), _T("High 优秀"), _T("Good 良好"),
+            _T("Medium 一般"), _T("Low 较差"), _T("Minimal 最低")
+        };
+        for (int i = 0; i < QUALITY_COUNT; i++)
+            SetDlgItemText(IDC_QLEVEL_LABEL_LEVEL0 + i, _L(kLevelNames[i]));
+        SetDlgItemText(IDC_QLEVEL_LABEL_HINT,
+            _TR("最大宽度 0 表示原始分辨率；DIFF/RGB565 适合局域网，H264 适合跨网"));
+        SetDlgItemText(IDC_QLEVEL_RESET, _TR("恢复默认"));
+        SetDlgItemText(IDOK,              _TR("确定"));
+        SetDlgItemText(IDCANCEL,          _TR("取消"));
+
         for (int i = 0; i < QUALITY_COUNT; i++) {
             m_working[i] = m_profiles[i];
         }
         LoadToControls();
-        TranslateDialog(this);
         return TRUE;
     }