feat(config): add CallbackBaseUrl to configuration for payment processing

- Introduced CallbackBaseUrl in both cms-config.yaml and appsettings.Staging.json to support dynamic callback URLs for payment processing.
- Updated PackageService to utilize the new CallbackBaseUrl for enhanced security and flexibility in payment integration.

src/CMSMicroservice.WebApi/Services/PackageService.cs

@@ -227,8 +227,13 @@ public class PackageService : PackageContract.PackageContractBase
             .FirstOrDefaultAsync(cancellationToken);
         
         // Callback URL از config — نه از ورودی کاربر (امنیت)
-        var frontOfficeBaseUrl = _configuration["FrontOfficeBaseUrl"] ?? "https://localhost:5268";
-        var callbackUrl = $"{frontOfficeBaseUrl}/profile/payment-callback?orderId={purchase.Id}";
+        // ۲۰کارت: CallbackBaseUrl اختیاری (مثلاً استیج → kbs2.ir چون دامنه استیج در ترمینال ثبت نیست)
+        var frontOfficeBaseUrl = isTwentyCard
+            ? (_configuration["TwentyCard:CallbackBaseUrl"]
+               ?? _configuration["FrontOfficeBaseUrl"]
+               ?? "https://localhost:5268")
+            : (_configuration["FrontOfficeBaseUrl"] ?? "https://localhost:5268");
+        var callbackUrl = $"{frontOfficeBaseUrl.TrimEnd('/')}/profile/payment-callback?orderId={purchase.Id}";
 
         var paymentGateway = _paymentGatewayResolver.Get(gatewayProvider);
         var payerName = $"{user?.FirstName} {user?.LastName}".Trim();