[qt_common] reorg + checkstate abstraction (#2735)

no diff. in functionality, just confirm builds on ubuntu 24.04/debian 12

Signed-off-by: crueter <crueter@eden-emu.dev>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/2735

src/qt_common/util/applet.h

@@ -0,0 +1,11 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef QT_APPLET_UTIL_H
+#define QT_APPLET_UTIL_H
+
+// TODO
+namespace QtCommon::Applets {
+
+}
+#endif // QT_APPLET_UTIL_H