Add end 2 end testing

Use https://github.com/bahmutov/feathers-chat-app as a test project

Start by reviewing the csrf-proxy repository and the linked feathers-chat-app test project to understand how the proxy handles sessions and CSRF tokens. Define an end-to-end test flow against that project, then verify that the flow runs successfully and catches authentication or CSRF regressions. The issue does not name files, test tools, or specific scenarios.

Written by the indexing model from the issue text.