chore: remove dead taskosaur/postgres/redis services, fix root user (#32)

- Remove taskosaur, postgres, redis services (zero Python references)
- Remove postgres-data, redis-data volumes
- Remove taskosaur env vars from dashboard and .env.example
- Change user: "0:0" to user: "" (override per-environment)
- Update header comments to reflect actual services
- celery-worker/openfang remain behind profiles
- Net: -93 lines of dead config

docker-compose.prod.yml

@@ -14,7 +14,6 @@
 #
 # Security note: Set all secrets in .env before deploying.
 #   Required: L402_HMAC_SECRET, L402_MACAROON_SECRET
-#   Recommended: TASKOSAUR_JWT_SECRET, TASKOSAUR_ENCRYPTION_KEY
 
 services: