fix: pin Node.js and pnpm versions in codegen Dockerfile

[dobrac]

Note

Low Risk
Build-environment-only changes; main risk is codegen differences or CI breakage due to the pinned Node/Python versions and new install method.

Overview
Updates the codegen build image to be more deterministic by pinning Node.js and pnpm versions and installing Node via the official tarball (with arch detection) instead of the NodeSource apt repo.

Also bumps the base runtime image from python:3.9 to python:3.10 for the Python stage.

^{Written by Cursor Bugbot for commit d279ec0. This will update automatically on new commits. Configure here.}

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Latest commit: d279ec0

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