Advance app runtime ownership and modernization docs

src/legacy_cloud_services.h

@@ -3,6 +3,8 @@
 #include "app_core/document_cloud.h"
 #include "foundation/result.h"
 
+#include <functional>
+
 class App;
 class NodeDialogCloud;
 
@@ -22,4 +24,6 @@ namespace pp::panopainter {
     pp::app::CloudDownloadSelectionAction action,
     NodeDialogCloud& dialog);
 
+void queue_legacy_cloud_worker_task(std::function<void()> task);
+
 } // namespace pp::panopainter