feat: production hardening (hop admission, reload, defaults) - #15

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, azure/setup-helm@v4, yokawasa/action-setup-kube-tools@v0.11.2. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/