Add missing admin backend endpoints:
- User management: list users (paginated/filterable), user detail view, update user status
- KYC approval: pending KYC queue, approve/reject KYC with comments
- Bulk moderation: approve/reject multiple listings in one request
- Domain events for KYC lifecycle (approved/rejected)
- Unit tests for all new handlers (35 tests passing)
All endpoints protected by ADMIN role guard via JwtAuthGuard + RolesGuard.
Co-Authored-By: Paperclip <noreply@paperclip.ing>