feat(sorting): implement ApplyOrderWithInStockPriority method for enhanced product sorting

- Added ApplyOrderWithInStockPriority method to prioritize in-stock products in queries.
- Updated GetDiscountProductsQueryHandler and GetCustomerProductsByFilterQueryHandler to utilize the new sorting method, ensuring in-stock items are listed first followed by user-defined sorting or creation date.
- Improved overall query handling for product availability and sorting logic.

src/CMSMicroservice.Application/Common/Extensions/SortByExtensions.cs

@@ -1,3 +1,4 @@
+using System.Linq.Expressions;
 using System.Linq.Dynamic.Core;
 using CMSMicroservice.Domain.Common;
 
@@ -16,6 +17,21 @@ public static class SortByExtensions
         return source.OrderBy(NormalizeSortBy(sortBy));
     }
 
+    /// <summary>
+    /// موجودی‌دارها اول، سپس سورت درخواستی کاربر (یا Created desc اگر SortBy خالی باشد).
+    /// </summary>
+    public static IQueryable<TSource> ApplyOrderWithInStockPriority<TSource>(
+        this IQueryable<TSource> source,
+        string? sortBy,
+        Expression<Func<TSource, bool>> isInStock) where TSource : BaseAuditableEntity
+    {
+        var ordered = source.OrderByDescending(isInStock);
+        if (string.IsNullOrWhiteSpace(sortBy))
+            return ordered.ThenByDescending(p => p.Created);
+
+        return ordered.ThenBy(NormalizeSortBy(sortBy));
+    }
+
     /// <summary>
     /// Dynamic LINQ treats "-Created" as unary minus on DateTime (invalid).
     /// Project convention: leading '-' means descending sort.

src/CMSMicroservice.Application/DiscountShopCQ/Queries/GetDiscountProducts/GetDiscountProductsQueryHandler.cs

@@ -57,10 +57,8 @@ public class GetDiscountProductsQueryHandler : IRequestHandler<GetDiscountProduc
             query = query.Where(p => p.Price <= request.MaxPrice.Value);
         }
 
-        if (!string.IsNullOrEmpty(request.SortBy))
-            query = query.ApplyOrder(request.SortBy);
-        else
-            query = query.OrderByDescending(p => p.Created);
+        // موجودی‌دارها اول، سپس سورت درخواستی
+        query = query.ApplyOrderWithInStockPriority(request.SortBy, p => p.RemainingCount > 0);
 
         var totalCount = await query.CountAsync(cancellationToken);
 

src/CMSMicroservice.Application/ProductsCQ/Queries/GetCustomerProductsByFilter/GetCustomerProductsByFilterQueryHandler.cs

@@ -67,11 +67,8 @@ public class GetCustomerProductsByFilterQueryHandler : IRequestHandler<GetCustom
         if (request.IsActive.HasValue)
             query = query.Where(x => x.IsDeleted != request.IsActive.Value);
 
-        // Apply sorting
-        if (!string.IsNullOrEmpty(request.SortBy))
-            query = query.ApplyOrder(request.SortBy);
-        else
-            query = query.OrderByDescending(x => x.Created);
+        // موجودی‌دارها اول، سپس سورت درخواستی
+        query = query.ApplyOrderWithInStockPriority(request.SortBy, x => x.RemainingCount > 0);
 
         // Pagination
         var totalCount = await query.CountAsync(cancellationToken);