Installing on an organization from the personal setup button now works

Before, we refused the mismatch and recorded nothing, but GitHub had already installed the app, so retrying only led to GitHub's "already installed" settings page and left you on an empty dashboard with no way forward. The organization is still subject to the usual access check: if it already belongs to someone else's Sinatra workspace, you are sent to request access rather than joined automatically. Installing on a different person's GitHub account is still refused.