feat(payment): enhance TwentyCard payment integration and update configuration

- Added support for optional Email and NationalId fields in PaymentRequest for TwentyCard transactions.
- Updated TwentyCardPaymentService to handle multipart/form-data requests and improved error handling.
- Modified appsettings and configuration files for both production and staging environments to include updated BaseUrl and credentials for TwentyCard.
- Updated README to reflect the new documentation location.

src/CMSMicroservice.Application/Common/Interfaces/IPaymentGatewayService.cs

@@ -108,6 +108,16 @@ public class PaymentRequest
     /// شماره فاکتور / سفارش
     /// </summary>
     public string Invoice { get; set; } = string.Empty;
+
+    /// <summary>
+    /// ایمیل (اختیاری — برای ۲۰کارت)
+    /// </summary>
+    public string? Email { get; set; }
+
+    /// <summary>
+    /// کد ملی (اختیاری — برای ۲۰کارت)
+    /// </summary>
+    public string? NationalId { get; set; }
 }
 
 /// <summary>