Close the small coverage gaps left after the members app move:
- FamilyMembership.__str__ string representation
- FamilyAdmin.member_count display (with and without members)
- CSV import skips a row with an empty required field (was only
exercising the invalid-date path)
- MemberImportResult.successful_rows property
Coverage 98% -> 99% (69 tests). The only remaining uncovered lines are
the redundant re-link branch in MemberCsvImporter.import_row (131-132),
which is unreachable because update_or_create already sets member.user.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Bernard Siebens
4165729d61