feat(order): refactor order data mapping for improved clarity and structure

- Updated GetAllDiscountOrdersQueryHandler to enhance order data mapping by using a more structured approach with AdminOrderDto.
- Refactored user full name construction in GetCustomerOrderQueryHandler and GetCustomerOrdersQueryHandler to utilize UserDisplayName for better readability.
- Added necessary using directives for consistency across query handlers.

src/CMSMicroservice.Application/Common/UserDisplayName.cs

@@ -0,0 +1,29 @@
+namespace CMSMicroservice.Application.Common;
+
+/// <summary>
+/// نام نمایشی کاربر برای گزارش‌ها؛ اگر نام خالی باشد موبایل یا شناسه.
+/// </summary>
+public static class UserDisplayName
+{
+    public static string From(string? firstName, string? lastName, string? mobile, long userId)
+    {
+        var name = string.Join(" ",
+            new[] { firstName, lastName }.Where(s => !string.IsNullOrWhiteSpace(s)));
+
+        if (!string.IsNullOrWhiteSpace(name))
+            return name;
+
+        if (!string.IsNullOrWhiteSpace(mobile))
+            return mobile.Trim();
+
+        return userId > 0 ? $"کاربر {userId}" : "—";
+    }
+
+    public static string From(Domain.Entities.User? user)
+    {
+        if (user is null)
+            return string.Empty;
+
+        return From(user.FirstName, user.LastName, user.Mobile, user.Id);
+    }
+}