Add Node.js runtime support

[N3xusFour]

Summary

Add Node.js as a supported runtime alongside Deno and Bun.

Motivation

• Many npm packages still assume "real Node" and may have quirks with Bun/Deno
• High compatibility with existing JavaScript/TypeScript ecosystem
• Low implementation effort since npm dependency flow already exists

Implementation Plan

1. Extend Runtime enum and image selection

• Add RuntimeNode Runtime = "node" to models/models.go
• Add RUNTIME_IMAGE_NODE env var support in executor/docker.go

2. Create Node Dockerfile (services/runtime-node/Dockerfile)

FROM node:20-alpine

RUN addgroup -g 1000 nodeuser && \
    adduser -D -u 1000 -G nodeuser nodeuser

USER nodeuser
WORKDIR /workspace

COPY --chown=nodeuser:nodeuser runner.mjs /runtime/runner.mjs

ENTRYPOINT ["node", "/runtime/runner.mjs"]

3. Create Node runner (services/runtime-node/runner.mjs)

• Read stdin JSON (ExecutionInput)
• Set process.env from event.env
• Dynamic import user module from /workspace/${mainModule}
• Call await module.handler(event, context)
• Capture console methods for log collection
• Output ExecutionOutput JSON to stdout

4. Add dependency installation

• Add installNodeDependencies() function in executor/docker.go
• Use npm install similar to how Bun uses bun add

Effort Estimate

~0.5-1 day

Acceptance Criteria

• runtime: "node" accepted in setup request
• Node.js handler functions execute correctly
• npm dependencies install and are available at runtime
• Console logs are captured
• Works with gVisor sandboxing