This PR adds a small UI touch-up to the welcome page so we can introduce
the "Book Onboarding" over there, as well as adding it to the user menu
(both in the signed in and signed out states). The actual URL these
buttons take to will still be updated to the correct destination.
<img width="700" alt="Screenshot 2024-11-12 at 12 45 27"
src="https://github.com/user-attachments/assets/9933bf94-f57a-43e2-8da3-bfbfd9fd24d0">
Release Notes:
- N/A
