Close/Go back button for "Sign In" also in mobile/reduced screen

[Bitcoinera]

Is your feature request related to a problem? Please describe.

When I try to sign in in mobile but then I fail or I change my mind for some reason, I would like as an user to have a button to go back to Lunie without having to sign in.

Right now the only option available is to click on the Lunie logo, which is not great UX, because I needed a while to figure it out, for example.

Describe the solution you'd like

Put an x symbol just like the one you get when you open the navbar.

Describe alternatives you've considered

Additional context

Here a screenshot of how it now looks like the Sign In screen: