Retire completed migration worker and transfer OAuth to normal reporting worker

On git-prk-server, retire the completed legacy migration runtime and switch the normal reporting analyzer to the migration worker's current dedicated ChatGPT OAuth credentials. Preserve audit/import data and a private rollback copy of normal credentials; never log credential contents. Keep the normal daily schedule and queue isolation unchanged. Verified: migration service and importer inactive/masked; migration containers removed; manual wrapper blocked with its existing pause marker; migration OAuth validated and transferred to normal auth storage (UID/GID 1000, mode 0600), source auth removed; normal analyzer restarted and health HTTP 200 ready; coordinator readiness HTTP 200; normal default queue unchanged; daily timer enabled/active, next run 2026-10-27 03:00 UTC. Private original-normal-auth and unit backups: /srv/prk-reporting/retired-migration-20261026T074312Z. Remaining validation blocker: read-only coordinator default-lane preview exceeded its 20-second HTTP timeout. No remote retry or real model request performed. Acceptance still requires resolving/validating normal workflow preview or successful normal workflow execution; OAuth provider acceptance has not been live-tested.