Signup: Streamline and remove passwords

Simplify and streamline signup flow to use the current styling and reduce the number of steps.

As part of the simplification, we will remove passwords and move to a login code based system. This means we can remove password related flows (forgot/reset/update).

New flow will be:

Login form -> email -> click link -> done

And for signup:

Signup form -> email -> click link -> done

NB. To simplify the signup code/flow, we will no longer help create a workspace on account creation. This is not a problem as we are manually onboarding users at present.

Steps

1. Design
2. Page: session/new
3. Page: session/check-inbox
4. Page: signup/new
5. Email: Login link
6. Backend: Login automatically when in dev mode
7. Backend: Generate/validate login links
8. Backend: session/magic-link
9. Backend: session/magic-link?signup=true (let us do slightly different things on first login)
10. Remove old password related code