Feat: Implement H264 for Linux client with dynamic libx264 loading

macos/ScreenHandler.h

@@ -4,6 +4,7 @@
 #import <dispatch/dispatch.h>
 #import <IOKit/pwr_mgt/IOPMLib.h>
 #import "../client/IOCPClient.h"
+#import "../common/commands.h"  // QualityLevel, QualityProfile, ALGORITHM_*
 #include <vector>
 #include <atomic>
 #include <mutex>
@@ -33,11 +34,7 @@ struct BITMAPINFOHEADER_MAC {
 };
 #pragma pack(pop)
 
-// Screen algorithm constants
-#define ALGORITHM_GRAY    0
-#define ALGORITHM_DIFF    1
-#define ALGORITHM_H264    2
-#define ALGORITHM_RGB565  3
+// Algorithm constants from commands.h: ALGORITHM_GRAY, ALGORITHM_DIFF, ALGORITHM_H264, ALGORITHM_RGB565
 
 class ScreenHandler : public IOCPManager {
 public: