[STAR-3767] Navigation Fixes

Jira ticket

Story

"As a Listaflow developer, I want to make redirect the app signup page to the marketing site sign up page."

Full description

Right now two different pages show when "sign up" is selected on the public site and on the app:

1. The "Join Beta" page shows on the public site
2. The registration page shows on the app

We need to ensure that there is a single point of access for signup. For now we want to redirect users to the "Join Beta" page instead of this registration page.

Completion criteria

• Signup: have one sign up page

Documentation updates & improvements criteria

• Left to the assignee’s appreciation