fix(gui): guard unused showTrayPopup position on macOS

The position parameter is only unused in the macOS branch, so scope the
annotation there with Q_UNUSED instead of [[maybe_unused]] on the signature.

Assisted-by: Claude Code:claude-opus-4-8
Signed-off-by: Camila Ayres <camila.ayres@nextcloud.com>

Author: camilasan

src/gui/systray.cpp

@@ -212,6 +212,7 @@ void Systray::showTrayPopup(WindowPosition position)
     }
 
 #ifdef Q_OS_MACOS
+    Q_UNUSED(position)
     if (showMacOSTrayPopup(geometry())) {
         setIsOpen(true);
         UserModel::instance()->fetchCurrentActivityModel();