Allow Capybara test server host in HostAuthorization

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>

config/environments/test.rb

@@ -58,4 +58,7 @@ Rails.application.configure do
   # config.action_view.annotate_rendered_view_with_filenames = true
 
   config.log_level = :info
+
+  # Allow Capybara's dynamic test server host (127.0.0.1:<random_port>)
+  config.hosts << '127.0.0.1'
 end