Create DDHH_JM_Admin_UI class with custom columns for job_offer admin listing:
- Anbieter (provider org name + contact person from user meta)
- Standort (location from ACF field)
- Art (job type from ACF field)
- Eingereicht am (submission date)
Removed default author/date columns to reduce clutter. Made columns sortable for efficient moderation workflow.
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
