Prompt user to change credentials when auth error happens in the background

This already happens when checking for updates via Get Blank Forms and will also happen for background checks that happen with Match Exactly enabled.

**Acceptance**
- [ ] Given Previously Downloaded Only is enabled
When the automatic check happens
And there is an authentication error (401)
Then I see a notification with an error message
When I click on the notification
Then I am prompted to enter my credentials again on the Get Blank Form page

Start with the existing Get Blank Forms behavior described in the issue and trace the automatic check when Previously Downloaded Only and Match Exactly are enabled. Verify the 401 path shows a notification, and that selecting it opens Get Blank Form with a prompt to re-enter credentials.

Written by the indexing model from the issue text.