Show visual feedback on pending login or login error

When testing, I was getting frustrated by the lack of feedback of the login page:

• When clicking submit on the form, the fields of the form were emptied and it was staying like this for a second before redirecting to the app page.
• When an error occurred on submit, the fields of the form were emptied and nothing was presented to the user to tell that something went wrong.

I made some quick improvements to have minimal feedback:

• when log in is pending:

• when there was an error: