Fix almost every warning (#2195)

Fix almost every warning as of Clang 19

* <codecvt> is deprecated, we can use QString's UTF-16 conversion
  instead
* remove sem_timedwait implementation as we don't need it anymore
* remove a useless shift that has its result discarded
* change usages of deprecated sprintf to snprintf

src/frontend/qt_sdl/CameraManager.cpp

@@ -59,6 +59,8 @@ void CameraFrameDumper::present(const QVideoFrame& _frame)
     case QVideoFrameFormat::Format_NV12:
         cam->feedFrame_NV12((u8*)frame.bits(0), (u8*)frame.bits(1), frame.width(), frame.height());
         break;
+    default:
+        break;
     }
 
     frame.unmap();