Create landing page and sign up/log in forms

Note this issue is **blocked** pending the implementation of AuthProvider in issue #28.

## Story
**AS A** Transplant Games supporter/participant,
**I WANT** to be able to read about the Transplant Games,
**SO THAT** I know what I am signing up for.

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## Details

Parent issue for landing page and log in/sign up forms.

We need a landing page so that logged out users can see information about registering for the Transplant Games before they sign up/log in.

- The page should link back to the [Transplant Australia website](https://transplant.org.au/)
- If the user is not signed in, they should be prompted to sign up or log in
- The page should contain a short description about registration, similar to this page from the [2024 Australian Transplant Games](https://australiantransplantgames.com/participate/registration/)
- The user should be able to find contact info and quick links for Transplant Australia

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## Acceptance criteria

A landing page that displays the following components:
- [x] A header/navbar #2 where:
- Users can click to return to the Transplant Australia website
- Users can click to log in or sign up

- [ ] A footer #3 with:
- A column for contact info for Transplant Australia
- A column for quick links for the Australian Transplant Games

- [ ] The body of the page #4 containing:
- A short description of the Australian Transplant Games in the centre of the page.

- [x] A sign up form #5 with:
- Email + password fields
- Sign up with Google

- [x] A log in form #6 with:
- Email + password fields
- Log in with Google
- Forgot password link