- Add new GET endpoint for retrieving a specific training run by run_id
- Validate run_id format with regex pattern ^[a-zA-Z0-9_-]+$ before DB access
- Return HTTP 400 for invalid run_id format, HTTP 404 for non-existent runs
- Ensure DELETE endpoint validation is correctly placed before any DB access
- Both endpoints now provide consistent security validation
- Mark task 5.8 as completed
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>