fix: clean-up-ci-cafe-port-3000-on-error

[Zaimwa9]

Thanks for submitting a PR! Please check the boxes below:

• I have added information to docs/ if required so people know about the feature!
• I have filled in the "Changes" section below?
• I have filled in the "How did you test this code" section below?
• I have used a Conventional Commit title for this Pull Request

This PR fixes an issue where E2E test retries would hang because port 3000 was still busy with a previous failed attempt.

TestCafe failed during initialization (one concurrent browser failed). There was no error handler and the CI retry wouldn't clean up the port.

The error was in the child process, the parent had no error handler, so it just exited without a proper error code which CI considered a success

Changes

• Added a proper error handling on café initialization (e2e/index.cafe.js)
• Clean up port 3000 in between attempts (.github/workflows/.reusable-docker-e2e-tests.yml)

How did you test this code?

With failing testcafe config:

module.exports = {
    "browsers": "test:headless",
    browserInitTimeout: 1,
    ...
    ...
}

[cursor]

You have run out of free Bugbot PR reviews for this billing cycle. This will reset on January 10.

To receive reviews on all of your PRs, visit the Cursor dashboard to activate Pro and start your 14-day free trial.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Review	Updated (UTC)
flagsmith-frontend-preview	Ready	Preview, Comment	Dec 18, 2025 9:24am
flagsmith-frontend-staging	Ready	Preview, Comment	Dec 18, 2025 9:24am

1 Skipped Deployment

Project	Deployment	Review	Updated (UTC)
docs	Ignored		Dec 18, 2025 9:24am

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-api-test:pr-6430	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-e2e:pr-6430	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api:pr-6430	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-6430	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-frontend:pr-6430	Finished ✅	Results ✅

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.06%. Comparing base (d5fbcd7) to head (b959cfb).
⚠️ Report is 15 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6430   +/-   ##
=======================================
  Coverage   98.06%   98.06%           
=======================================
  Files        1292     1292           
  Lines       46509    46509           
=======================================
  Hits        45611    45611           
  Misses        898      898           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.