Adapter Observer service

Standalone read-only analytics service for adapter-1c operational telemetry.

Run locally with:

ONEC_OBSERVER_AUDIT_DIR=<directory-with-adapter-audit.jsonl> python observer_server.py

The production compose definition and operational contract are in core/deploy/docker/adapter-observer/ and docs/runbooks/adapter-observer.md respectively. Do not make this service a dependency of the adapter or give it SQL credentials.