Why:
- tests/e2e/ cannot reach fixtures defined in a per-boundary conftest, and
`pytest_plugins` is only honoured in the root conftest.
Changes:
- move the Postgres/MinIO/Qdrant container fixtures into
tests/support/containers.py and register it as a root plugin
- fold MinIO bucket creation into `minio_settings`; an autouse fixture in a
globally registered plugin would pull a container into unit runs
- add a `postgres_settings` fixture so a component can be built from it directly
Impact:
- no behavior change; `pytest -m unit` still needs no Docker
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
