Add local Docker Compose workflow and ARM-friendly Docker build

[MrInterBugs]

Summary

This PR makes the local Docker workflow easier to use and improves compatibility on Apple Silicon Macs.

Changes

• add a simple docker-compose.yml for running the simulator locally
• document the Docker workflow in README.md
• update Dockerfile to use ENV key=value format
• only install libc6-i386 on amd64, so the image builds on Apple Silicon or any other ARM device

Notes

• this is intended to improve the local simulator workflow

How To Test

cd sunriser
docker compose up --build -d
curl http://localhost:9000
docker compose down