fix(config-service): implement GET /v1/config/history and POST /v1/config/secrets/reveal - #840

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@8ade135a41bc03ea155e62e844d188df1ea18608. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/