AML Settings: Credential Check & Clearer Messaging

The AML verification settings in Gateway Settings (Account → Gateway) have been enhanced with improved messaging and credential validation.

A new "Check" button below the API key and API secret fields validates the credentials and shows the connection status. A successful connection displays the number of remaining AML checks; invalid credentials show an error message.

Transaction Details: Underpayment Difference Highlighted

Transaction details now display the difference from the requested price when an underpayment occurs. The difference amount helps users quickly identify how much additional payment is required to complete the transaction.