## ADDED Requirements

### Requirement: Device Batch Series Binding Range Allocation Hint

The device batch series binding dialog SHALL provide a derived allocation-count hint for device-number range selection.

The hint MUST appear immediately below the `virtual_no_start` and `virtual_no_end` inputs.

The count MUST be computed as `结束设备号 - 起始设备号 + 1` using the same numeric range values accepted by the dialog.

#### Scenario: Show allocation count for a valid device-number range

- **GIVEN** 用户打开“批量设置设备套餐系列绑定”弹窗
- **AND** 用户选择 `selection_type="range"`
- **WHEN** 用户输入 `virtual_no_start` 和 `virtual_no_end`，且计算结果为正整数
- **THEN** 弹窗 MUST 显示 `共分配xxx台设备`
- **AND** `xxx` MUST 等于 `结束设备号 - 起始设备号 + 1`
- **AND** 当任一端点变化时，提示 MUST 立即更新

#### Scenario: Hide count hint for incomplete or invalid device-number ranges

- **GIVEN** 用户选择 `selection_type="range"`
- **WHEN** 任一起止设备号为空、无法按有效数值范围计算，或计算结果小于 `1`
- **THEN** 弹窗 MUST NOT 显示误导性的分配数量提示
