feat(api): implement GDPR-compliant user data deletion
- Add deletedAt/deletionScheduledAt fields to User model with indexes
- Implement 5 CQRS command handlers:
- RequestUserDeletion: 30-day soft-delete grace period
- CancelUserDeletion: restore within grace period
- ForceDeleteUser: admin immediate deletion with PII anonymization
- ProcessScheduledDeletions: cron-ready batch processor
- ExportUserData: GDPR Article 20 data portability
- Cascade strategy: anonymize PII, expire listings, cancel subscriptions,
delete reviews/inquiries/searches/notifications, preserve payments for audit
- Add UserDataController with DELETE /users/me, POST /users/me/cancel-deletion,
GET /users/me/export, DELETE /users/:id/force (admin)
- 22 unit tests covering all handlers (160 files, 853 tests passing)
- Migration: 20260410000000_add_user_soft_delete_fields
Co-Authored-By: Paperclip <noreply@paperclip.ing>