## ADDED Requirements

### Requirement: Refund Detail Inline Voucher Preview

The system SHALL display refund voucher images directly in the refund detail page when voucher file keys exist, and each displayed image SHALL support click-to-enlarge preview. Refund voucher viewing from the refund list SHALL be controlled by the permission code `refund:view_voucher`.

#### Scenario: Display and enlarge refund voucher in detail

- **GIVEN** 用户打开退款详情页
- **AND** 退款详情数据包含一个或多个退款凭证文件 key
- **WHEN** 页面渲染退款凭证区域
- **THEN** 系统 MUST 直接展示对应的凭证图片
- **AND** 用户点击任一凭证图片后，系统 MUST 放大预览该图片

#### Scenario: Hide voucher images when no voucher exists

- **GIVEN** 用户打开退款详情页
- **WHEN** 退款详情数据不包含退款凭证文件 key
- **THEN** 系统 MUST NOT 展示空的凭证图片占位
- **AND** 系统 MAY display `-` or equivalent empty-state text for the voucher field

#### Scenario: Show refund voucher list action with permission

- **GIVEN** 用户正在查看退款管理列表
- **AND** 某条退款记录存在 `refund_voucher_key`
- **AND** 当前用户拥有 `refund:view_voucher` 权限编码
- **WHEN** 系统渲染该行操作列
- **THEN** 系统 MUST show the `查看退款凭证` action

#### Scenario: Hide refund voucher list action without permission

- **GIVEN** 用户正在查看退款管理列表
- **AND** 某条退款记录存在 `refund_voucher_key`
- **AND** 当前用户不拥有 `refund:view_voucher` 权限编码
- **WHEN** 系统渲染该行操作列
- **THEN** 系统 MUST NOT show the `查看退款凭证` action

### Requirement: Refund Application Paid Order Filtering

The system SHALL restrict the order number search/select request in create refund application to paid orders by including `payment_status: 2` in the query parameters.

#### Scenario: Search selectable orders for refund application

- **GIVEN** 用户正在创建退款申请
- **WHEN** 用户通过订单号搜索/选择订单
- **THEN** 系统 MUST call the order search/list API with `payment_status: 2`
- **AND** 未支付、已取消或其他非已支付状态订单 MUST NOT be returned as selectable refund orders by the frontend query

### Requirement: Refund Application Zero Amount

The system SHALL allow the requested refund amount in create refund application to be `0`, while still preventing negative amounts and amounts greater than the actual received amount.

#### Scenario: Submit zero requested refund amount

- **GIVEN** 用户正在创建退款申请
- **AND** 用户已选择可退款订单
- **WHEN** 用户输入申请退款金额 `0`
- **THEN** 系统 MUST allow the amount validation to pass
- **AND** 系统 MUST submit `requested_refund_amount` as `0`

#### Scenario: Block negative requested refund amount

- **GIVEN** 用户正在创建退款申请
- **WHEN** 用户输入小于 `0` 的申请退款金额
- **THEN** 系统 MUST prevent submission
- **AND** 系统 MUST 提示申请退款金额不能小于 `0`

#### Scenario: Block requested refund amount above actual received amount

- **GIVEN** 用户正在创建退款申请
- **AND** 已选订单存在实收金额
- **WHEN** 用户输入的申请退款金额大于实收金额
- **THEN** 系统 MUST prevent submission
- **AND** 系统 MUST 提示申请退款金额不能大于实收金额

### Requirement: Refund Management Multi Image Voucher Upload

The system SHALL allow multiple refund voucher images in any browser-recognized image format to be uploaded in refund management and SHALL submit all uploaded file keys in the `refund_voucher_key` parameter as a comma-separated string.

#### Scenario: Submit multiple uploaded voucher images

- **GIVEN** 用户正在退款管理中创建或提交退款相关记录
- **AND** 用户上传了多张退款凭证图片
- **WHEN** 每张图片上传成功并返回文件 key
- **AND** 用户提交表单
- **THEN** 系统 MUST join the uploaded file keys with English commas
- **AND** 系统 MUST put the joined string into `refund_voucher_key`
- **AND** `refund_voucher_key` MUST look like `attachments/a.jpg,attachments/b.jpg` when multiple files exist

#### Scenario: Upload any image format refund voucher without frontend size limit

- **GIVEN** 用户正在创建退款申请
- **WHEN** 用户选择或拖入任意浏览器识别为图片类型的退款凭证
- **THEN** 系统 MUST NOT reject the file based on frontend file size checks
- **AND** 系统 MUST accept the file when its MIME type starts with `image/`

#### Scenario: Submit single uploaded voucher image

- **GIVEN** 用户正在退款管理中创建或提交退款相关记录
- **AND** 用户只上传了一张退款凭证图片
- **WHEN** 用户提交表单
- **THEN** 系统 MUST put that single file key into `refund_voucher_key` without a trailing comma

#### Scenario: Block submission without required voucher image

- **GIVEN** 退款管理表单要求上传退款凭证
- **WHEN** 用户未上传任何凭证图片并尝试提交
- **THEN** 系统 MUST prevent submission
- **AND** 系统 MUST 提示用户上传退款凭证