SEV-3: reported, blocks only with --strict

Nothing checks that a change did not break login

What goes wrong

A small fix goes live on Friday and signup is broken until Monday.

Add one test for each money path: sign up, log in, and pay. Run them on every pull request.

npx sigship

Run it in your project. It reports this check as no-tests, along with 16 others. Nothing leaves your machine.