fix(ci): switch healthcheck to wget and update Node.js to v20

[codxbrexx]

Summary

This PR fixes the silent failure of the FaaS test container readiness check and bumps the CI environment to use the current Active LTS version of Node.js.

• docker-compose.yml: Switched the healthcheck command from curl to wget. curl is not installed in the faas production runtime image, causing the healthcheck to constantly fail with sh: curl: not found. Added a service_healthy condition so tests wait for the server.
• ci.yml: Updated setup-node action to use Node.js version 20 instead of 18 (which reached End-of-Life in April 2025). This ensures tests run against a supported runtime.
• test.sh: Replaced hardcoded localhost URL with ${FAAS_URL:-http://localhost:9000}.

Related issue

• Extracted from Fix/ci integration tests #122
• Testing Requirement: Solves the existing CI integration tests, which were previously failing to start due to a broken healthcheck (sh: curl: not found).

Type of change

• Bug fix
• New feature
• Documentation
• Chore / CI
• Breaking change

How to test

1. Checkout the branch fix/ci-healthcheck
2. Run sudo docker compose down --remove-orphans && sudo docker compose up --build --exit-code-from test
3. Verify that the initial healthcheck passes using wget and the test container boots successfully instead of failing on the unhealthy dependency.

Checklist

• I have read the contributing guidelines
• I added tests that prove my fix is effective or that my feature works
• I updated documentation if necessary

Notes for reviewers

Node 18 is EOL and no longer receiving security updates, so upgrading the CI environment to Node 20 aligns with GitHub Actions' recommended runner environments and prevents deprecation warnings.

Release notes

Fixed Docker Compose test container healthcheck and updated CI environment to Node.js v20.