Negative Commission Rates Accepted

Describe the bug
An issue has been identified in the Multivendor Admin Dashboard where the commission rates for vendors are accepting negative values.

To Reproduce
Steps to reproduce the behavior:

Log in to the Multivendor Admin Dashboard.
Navigate to the section where commission rates for vendors are configured.
Attempt to set a negative value for the commission rate.
Expected behavior
The system should prevent users from entering or saving negative values for commission rates, as negative rates are not valid in this context.

Screenshots
https://github.com/ninjas-code-official/food-delivery-multivendor/assets/152266796/1cbcd911-8f36-43bc-8de1-8498ea3b5a78

Desktop:

Browser: chrome

首先定位用于配置供应商佣金率的 Multivendor Admin Dashboard 入口点，并在 Chrome 中复现负值行为。当负佣金率被拒绝且无法保存时，工作即告完成；如果该处已有测试，请添加或更新相关的验证覆盖。

由索引模型根据 Issue 内容生成。