MVP: Job status API endpoint

[acgetchell]

Description

Implement /status/{job_id} endpoint in FastAPI controller.

Tasks

• Complete main.py status endpoint implementation
• Query database for job status
• Check SLURM status using sacct/squeue
• Return standardized status response
• Add proper error handling for not found jobs

Acceptance Criteria

• GET /status/{job_id} returns current job state
• Status includes: queued, running, completed, failed
• Timestamps for each state transition included