Implement 404 Error state for users signed into Cal-ITP Benefits Administrator

[indexing]

The Cal-ITP Benefits application currently has a 404 error view.

The current 404 error view has a couple problems now that we have introduced the admin interface and a new set of users.

• Its styling aligns with the rider-facing application.
• The return home button goes to the rider-facing home view.

In a nutshell, the design is intended for transit riders only; it doesn't account for admin users.

We need a 404 error view for admin users that have authenticated with the application.