Improve signup page UX

[ruilopesm]

• Refactor it into a multi step form. Where the first step consists of the QR scanning and the second one of the data inputs themselves.

• Add descriptive error messages (safira should send them).

• There should be a close button on the QR scanning window.

[pravintargaryen]

@ruilopesm Please assign this to me

[ruilopesm]

@pravintargaryen Assigned. Thanks for wanting to contribute.