[Beginner]: Refactor Workday API URL building into a helper function

Description

In fetch_workday_jobs, the logic to extract the tenant and site ID from a workday URL is bulky. Extract this logic into a pure helper build_workday_api_url(host, site_path).

Why it matters

Isolating URL parsing logic into an independent function makes it vastly easier to write unit tests for edge cases.

Acceptance Criteria

• [ ] Extract URL generation to a new helper function
• [ ] Call the helper function from within the main fetch loop
• [ ] Passes pre-commit run --all-files