Advanced AI Prompt for Node.js Microservices with Tini Initialization

Act as a Kubernetes Reliability Engineer. Write a hardened Dockerfile for a Node.js microservice that explicitly incorporates 'tini' (v[TINI_VERSION]) as the PID 1 init process. The Dockerfile must be multi-staged and execute under a non-root user within [APP_DIR] for security compliance. Set [NODE_ENV] to production and expose [PORT]. Provide a technical explanation in the comments of why using tini is absolutely critical for Node.js containers in a Kubernetes environment to properly handle signal forwarding (SIGTERM) and reap zombie processes.