* Move from env variables to SiteConfig
Related to #5384
This PR only deals with the first remaining part outlined in the issue, starting to use existing SiteConfig keys instead of the env variables.
* Restore Envfile to original version for now
* Add registration view to sign_in page
* Add better sad path for failed sign ins/ups
* Ensure email is downcased for authorization
* Remove .downcase for emails
* Use partial for styles
