RecoverStuckTasks now skips tasks that already have a slurm_job_id,
and ProcessTask adds a guard before the submitting step to prevent
re-submission even if a task is incorrectly re-enqueued.
Also deprecates POST /api/v1/jobs/submit endpoint (replaced by POST /tasks)
and comments out related handlers and tests.
- Comment out SubmitApplication handler method
- Comment out route registration in server.go (interface + router + placeholder)
- Comment out related handler tests
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>