Feat: Re-create Login Screen Using Tailwind CSS

With `Tailwind CSS` now being available by `default` in `Phoenix 1.7` we might as well adopt it in `Auth` ... 💭

This is what `auth v1` looks like at the time of writing: https://auth.dwyl.com

We can definitely tidy up this copy for consistency. Just using this as a guide for layout.

Drawing inspiration from:

https://github.com/davidgrzyb/tailwind-login-template

https://tailwind-elements.com/docs/standard/forms/login-form/

https://flowbite.com/blocks/marketing/login

I expect this to take me a few hours cause I'm no `Tailwind` (or `CSS`) expert. ⏳