Dagu: Path traversal in DAG creation allows arbitrary YAML file write outside DAGs directory

The CreateNewDAG API endpoint POST /api/v1/dags does not validate the DAG name before passing it to the file store. While RenameDAG calls core.ValidateDAGName to reject names containing path separators line 273 in dags.go, CreateNewDAG skips this validation entirely and passes user input directly...