- document the microservice topology, ingress-exposed vs. internal-only
  services, the shared Postgres/RabbitMQ/Redis-Dragonfly data layer
  (incl. the shared bpmn database and filestorage's dual DB/S3 backend),
  and a C4 container diagram of cross-service connections
- link README.md to the new ARCHITECTURE.md
- add a README to every component with its dev-cycle commands and the
  service dependencies that touch it in the C4 diagram