[feat] add Windows privacy screen and prefer DXGI capture

apps/desktop/src/platform/windows/windows_thread_dpi.h

@@ -0,0 +1,53 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2026-09-10
+ * Copyright (c) 2026 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _WINDOWS_THREAD_DPI_H_
+#define _WINDOWS_THREAD_DPI_H_
+
+#include <Windows.h>
+
+namespace crossdesk {
+
+// Keep newer DPI entry points out of the import table: privacy capability
+// checks must still be able to report unsupported on pre-2004 Windows.
+class ScopedWindowsPhysicalCoordinates {
+ public:
+  using SetContext = DPI_AWARENESS_CONTEXT(WINAPI*)(DPI_AWARENESS_CONTEXT);
+  ScopedWindowsPhysicalCoordinates() {
+    setter_ = reinterpret_cast<SetContext>(GetProcAddress(
+        GetModuleHandleW(L"user32.dll"), "SetThreadDpiAwarenessContext"));
+    if (setter_) {
+      previous_ = setter_(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
+      // Ordinary remote input retains compatibility with Windows 10 1607.
+      // The privacy backend itself requires build 19041 before using this.
+      if (!previous_)
+        previous_ = setter_(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE);
+    }
+  }
+  ~ScopedWindowsPhysicalCoordinates() {
+    if (setter_ && previous_) setter_(previous_);
+  }
+  ScopedWindowsPhysicalCoordinates(const ScopedWindowsPhysicalCoordinates&) =
+      delete;
+  ScopedWindowsPhysicalCoordinates& operator=(
+      const ScopedWindowsPhysicalCoordinates&) = delete;
+  bool active() const { return previous_ != nullptr; }
+
+ private:
+  SetContext setter_ = nullptr;
+  DPI_AWARENESS_CONTEXT previous_ = nullptr;
+};
+
+inline UINT PrivacyWindowDpi(HWND hwnd) {
+  using GetDpi = UINT(WINAPI*)(HWND);
+  static const auto get_dpi = reinterpret_cast<GetDpi>(
+      GetProcAddress(GetModuleHandleW(L"user32.dll"), "GetDpiForWindow"));
+  return get_dpi ? get_dpi(hwnd) : 96;
+}
+
+}  // namespace crossdesk
+
+#endif  // _WINDOWS_THREAD_DPI_H_