Harden Postgres bootstrap artifacts (#40) - #41

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11d5960a326750d5838078e36cf38b85af677262, actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff, docker/build-push-action@10e90e3645eae34f1e60eeb005ba3a3d33f178e8, docker/login-action@c94ce9fb468520275223c153574b00df6fe4bcc9, docker/setup-buildx-action@8d2750c68a42422c14e847fe6c8ac0403b4cbd6f, docker/setup-qemu-action@c7c53464625b32c7a7e944ae62b3e17d2b600130. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/