feat(payment): add per-user in-memory lock for gateway operations

Introduce IUserPaymentLock to serialize payment initiate and verify flows
per user, preventing concurrent duplicate gateway requests across services.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/CMSMicroservice.Application/Common/Exceptions/PaymentInProgressException.cs

@@ -0,0 +1,22 @@
+namespace CMSMicroservice.Application.Common.Exceptions;
+
+/// <summary>
+/// Thrown when a concurrent payment operation is already in progress for the same scope.
+/// </summary>
+public class PaymentInProgressException : Exception
+{
+    public PaymentInProgressException()
+        : base("یک عملیات پرداخت دیگر در حال پردازش است. لطفاً چند لحظه صبر کنید.")
+    {
+    }
+
+    public PaymentInProgressException(string message)
+        : base(message)
+    {
+    }
+
+    public PaymentInProgressException(string message, Exception innerException)
+        : base(message, innerException)
+    {
+    }
+}