Fix multiple redirects when logging in and the flicker/blank screen when logging out

[cstns]

Current Behavior

Logging in:

• a redundant authentication call is made after filling in your username/email and clicking login to move to the password page
• upon successful authentication the user is redirected twice causing the ui to stutter

Logging out:

• the user is redirected twice, once of which, a blank page causing the ui to flicker

Expected Behavior

The application should treat login and logout seamlessly

Steps To Reproduce

login and logout

Environment

• FlowFuse version: 2.4.0
• Node.js version: n/a
• npm version: n/a
• Platform/OS: n/a
• Browser: n/a

Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate

[cstns]

found during the implementation of #3825