feat: add PaymentTransaction table for gateway-level tracking

- New PaymentTransaction entity (Domain/Entities/Payment/) with all gateway fields:
  GatewayProvider, MerchantId, Authority, CardPan, CardHash, RefId, VerificationStatusCode, etc.
- New PaymentTransactionConfiguration with indexes on Authority, GatewayProvider, UserId, TransactionId, RefId
- Added DbSet<PaymentTransaction> to IApplicationDbContext and ApplicationDbContext
- Extended PaymentVerificationResult DTO with CardPan, CardHash, VerificationCode
- Updated ZarinPalPaymentService.VerifyPayment to return CardPan/CardHash/VerificationCode
- Updated all 5 payment consumers to create/update PaymentTransaction:
  * PlaceOrderCommandHandler — creates PaymentTransaction after InitiatePayment
  * PaymentCallbackController — updates PaymentTransaction after VerifyPayment
  * ChargeDiscountWalletCommandHandler — creates PaymentTransaction + fixed callback URL
  * VerifyDiscountWalletChargeCommandHandler — updates PaymentTransaction after verify
  * TransactionsService.CustomerPaymentRequest/Verification — create/update PaymentTransaction
  * PackageService.CustomerPurchasePackage/Verify — create/update PaymentTransaction
- Transaction table untouched — PaymentTransaction is a separate table
- Pattern inspired by PYMS: create row before gateway → update after verify
- EF migration: AddPaymentTransactionTable

src/CMSMicroservice.Application/DiscountShopCQ/Commands/PlaceOrder/PlaceOrderCommandHandler.cs

@@ -207,6 +207,25 @@ public class PlaceOrderCommandHandler : IRequestHandler<PlaceOrderCommand, Place
                 {
                     // ذخیره Authority/RefId در تراکنش برای verify بعدی
                     transaction.RefId = paymentResult.RefId;
+
+                    // ثبت PaymentTransaction — جدول جدید با اطلاعات درگاه
+                    var paymentTx = new PaymentTransaction
+                    {
+                        GatewayProvider = _configuration["PaymentProvider"] ?? "zarinpal",
+                        MerchantId = _configuration["ZarinPal:MerchantId"] ?? "",
+                        Amount = finalGatewayAmount,
+                        CallbackUrl = callbackUrl,
+                        Description = $"فروشگاه تخفیفی - سفارش #{order.Id}",
+                        Mobile = null,
+                        UserId = request.UserId,
+                        RequestStatusCode = 100,
+                        RequestStatusMessage = "Success",
+                        Authority = paymentResult.RefId,
+                        PaymentStatus = false, // هنوز verify نشده
+                        TransactionId = transaction.Id,
+                        OrderId = order.Id.ToString()
+                    };
+                    _context.PaymentTransactions.Add(paymentTx);
                     await _context.SaveChangesAsync(cancellationToken);
 
                     paymentUrl = paymentResult.GatewayUrl;