Capybara starts a Puma server on 127.0.0.1:<random_port> for system
tests. Rails HostAuthorization was blocking all requests from that host
since it was not in the config.hosts allowlist, causing every page to
return a blank 403 response and all system tests to fail.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>