[Eco Bounty] Missing validation – Allows negative input in Convert form

Wallet Address:
0x0f06443fbfc0Eb7D1f1c98DC74005546e2f70AAb

Bug Description:
In the Convert section of the dApp, users can input negative numbers (e.g., -2) as the token amount without triggering any validation or error message. The system accepts the value visually, which may lead to user confusion.

Device & Testing Environment:

• Device: Dell Laptop

• OS: Ubuntu

• Browser: Chrome

Steps to Reproduce:

1. Go to https://bridge.iotex.io

2. Click on the Convert tab or Bridge tab

3. In the amount input field, enter a negative number like -2

4. Observe: No warning or error is shown, and the input is accepted

Actual Result:
Negative values are accepted without any validation or UI feedback

Expected Result:

• Input field should only allow positive numbers greater than zero

• Display inline validation error when user enters a negative value

• Prevent submission or further interaction until corrected