Rewrite README with usage guide, deployment instructions, and protocol
docs. Update CLAUDE.md to reflect gomoku-only architecture. Add English
doc comments to all key server Go files, replacing Chinese comments.
Create docs/system-architecture.md (state machine, protocol, database
schema) and docs/deployment-guide.md (local dev, Docker, production
nginx, resource requirements).
Update Dockerfile to Go 1.22 with repo-root build context to include
web client. Update docker-compose to match.