add missing include

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: daschuer

src/engine/enginemixer.cpp

@@ -1,5 +1,6 @@
 #include "engine/enginemixer.h"
 
+#include <algorithm>
 #include <memory>
 
 #include "audio/types.h"