## 1. Implementation

- [x] 1.1 Update refund order creation request type to include required `refund_voucher_key: string`.
- [x] 1.2 Add refund voucher image upload to the refund order creation form using `/storage/upload-url`, storing the returned file key.
- [x] 1.3 Validate that refund voucher is uploaded before allowing refund order creation.
- [x] 1.4 Submit `refund_voucher_key` in the create refund order payload.
- [x] 1.5 Add a list operation to view the refund voucher when `refund_voucher_key` exists, matching the existing order list payment voucher behavior.
- [x] 1.6 Show the refund voucher directly in refund order details when `refund_voucher_key` exists.
- [x] 1.7 Verify create, list preview, and detail display flows manually or with existing tests.
