## Contact Deduplication

When creating contacts via upsert, the system checks for duplicates using the following field priority (first match wins):

1. `ln_member_id` (LinkedIn member ID)
2. `ln_id` (LinkedIn public ID)
3. `sn_id` (Sales Navigator ID)
4. LinkedIn nickname
5. `work_email`
6. `personal_email`
7. `name` + `company_name` combination