- Add admin_id FK to kontrakans table
- Add authorization checks to KontrakanController (edit, update, destroy, bulkDestroy)
- Add authorization checks to BookingController (store, bulkDestroy)
- Fix EnsureRole middleware to use auth:admin guard
- Fix booking index stats to filter by admin ownership
- Add model relationships: Admin.kontrakans(), Admin.isSuperAdmin(), Admin.isAdmin()
- Ensure admin biasa sees only their data, super_admin sees all data
- Secure bulk delete operations with per-item admin validation