Feature: Add power management to keep macOS client always responsive

macos/ScreenHandler.h

@@ -2,6 +2,7 @@
 
 #import <CoreGraphics/CoreGraphics.h>
 #import <dispatch/dispatch.h>
+#import <IOKit/pwr_mgt/IOPMLib.h>
 #import "../client/IOCPClient.h"
 #include <vector>
 #include <atomic>
@@ -132,4 +133,7 @@ private:
 
     // Input handler for mouse/keyboard control
     std::unique_ptr<InputHandler> m_inputHandler;
+
+    // Power management: prevent display sleep during remote desktop
+    IOPMAssertionID m_displayAssertionID;
 };