Replace soft-delete with anonymize + hard-delete to meet iOS App Store
data retention requirements. Non-PII fields are preserved in
anonymous_session_snapshots for analytics.
- Add anonymous_session_snapshots table and ORM model
- Implement anonymizer to extract non-PII fields before deletion
- Remove points_ledger.biz_id FK constraint (snapshot-style reference)
- Preserve transaction history while allowing session deletion
- Add 14 unit tests + 1 integration test
qzl