The plug was incorrectly placed in the endpoint, causing it to run on
all requests including APIs. Moved to :browser pipeline where it belongs,
and removed redundant fetch_session call since the pipeline handles it.
When Kubernetes performs rolling deployments, the old pod gracefully shuts down
and Oban's internal processes receive EXIT :shutdown signals. These are logged
as "unexpected" even though they're normal during shutdown.
Added custom logger filter to drop these messages in production:
- Oban.Queue.Watchman/Producer receiving EXIT :shutdown
- Oban plugin processes receiving EXIT :shutdown
- Reduces log noise during deployments without hiding real errors
The filter is production-only to preserve full debugging in development.
