Adds template, view, routing, and controller handling for the new first-run process

Closes #1794
- Adds the complete setup template using existing formatting as much as possible
- Adds complete styling for the setup template, reusing components where possible
- Adds the client view for setup, modeled after the /signup view with necessary changes
- Adds an admin controller method to handle setup, modeled after /signup with changes
- Adds routing for the new view
- Changes redirect when no user to /setup from /signup
- Adds routing tests