Align the coordinator with the master PLAN.md (CTX-00, CTX-04) and harden
process startup.
- CTX-00: freeze docs/api-contract.md as the v1 source of truth for the
Go coordinator and Python worker.
- CTX-04: worker registry — workers table (migration 0002), domain.Worker,
RegisterWorker use case, WorkerRepository, and POST /workers/register.
- Contract alignment: claim uses `capabilities` (was `workloads`),
COORDINATOR_TOKEN env (WORKER_AUTH_TOKEN kept as fallback), and
GET /health now reports database readiness (503 when the DB is down).
- Logging: logs are teed to stdout and an optional rotated file (LOG_FILE)
via lumberjack, so they survive a container rebuild.
- Startup resilience: the initial DB connection is retried with backoff,
so the coordinator waits for Postgres to boot instead of crash-looping.
Efremenko Arhip
dc92121acc