- Added duplicate detection and handling for pensions, pension_death, pension_separate, and pension_results imports
- Tracks (file_no, version) composite keys in-memory during import
- Checks database for existing records before insert
- Handles IntegrityError gracefully with fallback to row-by-row insertion
- Returns 'skipped' count in import results
- Prevents transaction rollback cascades that previously caused all subsequent rows to fail
- Consistent with existing rolodex duplicate handling pattern