frontend: fix APIv3 ordering
    
    The ordering didn't work because SQLAlchemy's `query.order_by`
    function expects its argument to be a model property and we were
    passing a string into it.
    
    Now if you run
    
        client = Client.create_from_config_file()
        pagination = {"limit": 10, "order": "id", "order_type": "DESC"}
        projects = client.project_proxy.get_list(pagination=pagination)
    
    the projects are correctly ordered by the newest one.