Start Document Intelligence Job
Validates the uploaded file and starts processing.
**Validation Checks:**
- File must be uploaded before starting
- File size must not exceed 200 MB
- PDF must be parseable by the PDF parser
- ZIP must contain only JPEG/PNG images
- ZIP must be flat (no nested folders beyond one level)
- ZIP must contain at least one valid image
- Page/image count must not exceed 10 (returns `422` with `max_page_limit_exceeded` if exceeded)
- User must have sufficient credits
**Processing:**
Job runs asynchronously. Poll the status endpoint or use webhook callback for completion notification.