Migrate team signup to React

[paolodamico]

Is your feature request related to a problem?

/signup/{token} is still a Django view, which means that the UX is not great (e.g. the error messages are shown in a small dark font which are easy to ignore, huge password requirements, etc.)

Describe the solution you'd like

I'd like this view to implemented in React to follow the general UX of the new org sign up page.

Describe alternatives you've considered

Keep the current version which is confusing and likely causing a drop in sign ups.

Additional context

Related to #2259 and reported again here.

Thank you for your feature request – we love each and every one!

[paolodamico]

This should also help with an edge case with session recordings in which we lose some snippets of time from login to using the app.

[timgl]

Agree on password requirements, i bet we're losing people due to that