feat(deploy): add Docker Compose self-hosting

[alexfrmn]

Summary

• add a non-root multi-stage Docker image
• add a three-service Compose stack for app, gateway, and persistent PTY owner
• preserve the PTY daemon loopback boundary by sharing the gateway network namespace
• persist workspace and SQLite data in named volumes
• document Docker deployment and update renamed repository links

Verification

• pnpm exec tsc --noEmit
• pnpm lint
• pnpm build
• git diff --check
• YAML parse of docker-compose.yml

Environment limitation

The cold-start worker has Docker CLI but no Compose plugin, and its Docker socket is inaccessible, so docker compose up and image build could not be executed here.