- groups-architecture and membership-fee-architecture docs
- Gettext: add/correct German for authorization and membership fee type
- membership_fee_helpers_test and membership_fee_status_test adjustments
- Remove Process.sleep calls from integration tests (tests run synchronously in SQL sandbox)
- Improve error handling: membership_fee_type_not_found now returns changeset error instead of just logging
- Clarify partial_failure documentation: successful_cycles are not persisted on rollback
- Update documentation: joined_at → join_date, left_at → exit_date
- Document PostgreSQL advisory locks per member (not whole table lock)
- Document gap handling: explicitly deleted cycles are not recreated
