Happy Coder is no longer used. Node.js was only installed as a
dependency for `npm install -g happy-coder`, so both are removed.
This shrinks the Docker image and simplifies the configuration.
Removed from: Dockerfile, Helm values/schema/templates, serverless
manifests, Makefile, and all documentation.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>