- Add orchestrator-staging compose service under profile 'staging'
so normal 'docker compose up -d' does NOT start it.
- Port 8501 via command override; network_mode: host (no ports mapping needed).
- DB isolation via separate volume ./data/staging:/app/data — physically
separate from prod ./data/orchestrator.db on the host.
- ORCH_DB_PATH=/app/data/orchestrator.db explicit in env (same container
path, isolated by volume mount).
- Add .env.staging.example with all required keys and placeholders.
- Update .gitignore: add .env.staging and data/staging/ exclusions.
- Add docs/STAGING.md: how to start staging, architecture table, roadmap.
Refs: ORCH-31 (Stage 1 of 5)