How can I customize the styling and layout of Universal Login templates using the Auth0 Management API or CLI?

I’m tasked with updating the appearance and structure of Universal Login templates, specifically altering the UI of input fields and buttons, rearranging elements within the auth:widget, and incorporating a header with a close button that redirects to my website upon clicking. How can I accomplish this level of customization using either the Management API or CLI? I aim to seamlessly integrate these modifications into the Universal Login experience while maintaining a smooth user flow. Any guidance or steps on achieving this would be greatly appreciated. Thank you!