refactor(extensions): improve sorting logic in ApplyOrder method

- Simplified the default sorting approach by directly returning the ordered source.
- Introduced NormalizeSortBy method to handle dynamic LINQ sorting, accommodating leading '+' and '-' for ascending and descending order respectively.
- Enhanced code clarity and maintainability by reducing unnecessary variable assignments.

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

@@ -8,16 +8,31 @@ public static class SortByExtensions
     public static IQueryable<TSource> ApplyOrder<TSource>(this IQueryable<TSource> source,
         string? sortBy) where TSource : BaseAuditableEntity
     {
-        // default sort approach
         if (sortBy is null or "")
         {
-            source = source.OrderByDescending(p => p.Created);
-            return source;
+            return source.OrderByDescending(p => p.Created);
         }
 
-        // sort using dynamic linq
-        source = source.OrderBy(sortBy);
+        return source.OrderBy(NormalizeSortBy(sortBy));
+    }
 
-        return source;
+    /// <summary>
+    /// Dynamic LINQ treats "-Created" as unary minus on DateTime (invalid).
+    /// Project convention: leading '-' means descending sort.
+    /// </summary>
+    private static string NormalizeSortBy(string sortBy)
+    {
+        sortBy = sortBy.Trim();
+        if (sortBy.StartsWith('-') && sortBy.Length > 1)
+        {
+            return $"{sortBy[1..]} descending";
+        }
+
+        if (sortBy.StartsWith('+') && sortBy.Length > 1)
+        {
+            return $"{sortBy[1..]} ascending";
+        }
+
+        return sortBy;
     }
 }