Add Dockerfile and Docker Compose for containerized setup

[aswinsuriya16]

This PR introduces Docker support for the project, enabling easy containerized development and deployment.

Changes introduced:

• Added a multi-stage Dockerfile for lightweight and secure builds.
• Configured .dockerignore to reduce image size.
• Added docker-compose.yml for simplified local setup.
• Updated README.md with Docker usage instructions (build, run, and compose).

Benefits:

• Developers can run the project without installing Node.js locally.
• Provides a consistent runtime environment across machines.
• Simplifies deployment using Docker-compatible platforms.
• Follows best practices (multi-stage build, non-root user, production mode).