[Beginner]: Make Workday API fetch limit configurable in `update_jobs.py`

Description

In fetch_workday_jobs, there is a hardcoded limit = 20 inside the pagination loop. Extract this to a parameter or constant.

Why it matters

Hardcoded limits can silently bottleneck performance if the API supports larger page sizes, or overwhelm the client if it doesn't.

Acceptance Criteria

• [ ] Extract limit = 20 to a constant WORKDAY_PAGE_LIMIT
• [ ] Use the constant in the payload
• [ ] Passes pre-commit run --all-files