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

### 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

No files or tests are named. Start by reproducing the login and logout flows described in the issue on FlowFuse 2.4.0, then trace the authentication and redirect entry points involved. Done means login and logout perform no redundant authentication call or second redirect, with no UI stutter, flicker, or blank page.

Written by the indexing model from the issue text.