Centralize retained dialog close bindings

src/node_usermanual.cpp

@@ -1,5 +1,6 @@
 #include "pch.h"
 #include "log.h"
+#include "legacy_ui_overlay_services.h"
 #include "node_usermanual.h"
 #include "layout.h"
 
@@ -16,7 +17,7 @@ void NodeUserManual::init()
     SetPositioning(YGPositionTypeAbsolute);
     add_child_file("data/dialogs/usermanual.xml", "usermanual");
     btn_ok = find<NodeButton>("btn-ok");
-    btn_ok->on_click = [&](Node*) { destroy(); };
+    pp::panopainter::bind_legacy_click_destroys_node(*btn_ok, *this);
 }
 
 kEventResult NodeUserManual::handle_event(Event* e)