feat: route UploadFinisher to dedicated queue
This separates UploadFinisher tasks from UploadProcessor tasks to prevent
lightweight finishing operations from being blocked by heavy processing work.
Key changes:
- Add explicit route for upload_finisher_task_name before the upload.* wildcard
- Default to the upload queue for backward compatibility (no k8s config = no change)
- When upload_finisher queue is configured, tasks route to upload_finisher
(or enterprise_upload_finisher for enterprise customers)
This change is safe to deploy before or after the k8s-v2 config changes.