Add migration for DiscountProductImages table

- Created a new table `DiscountProductImages` in the CMS schema.
- Added columns for image details including `Title`, `AltText`, `ImagePath`, `ThumbnailPath`, `SortOrder`, `IsActive`, `Created`, `CreatedBy`, `LastModified`, `LastModifiedBy`, and `IsDeleted`.
- Established a foreign key relationship with the `DiscountProducts` table.
- Created indexes on `DiscountProductId` and a composite index on `DiscountProductId` and `SortOrder`.

src/CMSMicroservice.Domain/Entities/DiscountShop/DiscountProduct.cs

@@ -83,4 +83,9 @@ public class DiscountProduct : BaseAuditableEntity
     /// دسته‌بندی‌های این محصول
     /// </summary>
     public virtual ICollection<DiscountProductCategory> ProductCategories { get; set; }
+    
+    /// <summary>
+    /// تصاویر گالری محصول
+    /// </summary>
+    public virtual ICollection<DiscountProductImage> Images { get; set; }
 }

src/CMSMicroservice.Domain/Entities/DiscountShop/DiscountProductImage.cs

@@ -0,0 +1,47 @@
+namespace CMSMicroservice.Domain.Entities.DiscountShop;
+
+/// <summary>
+/// تصویر گالری محصول تخفیفی
+/// </summary>
+public class DiscountProductImage : BaseAuditableEntity
+{
+    /// <summary>
+    /// شناسه محصول
+    /// </summary>
+    public long DiscountProductId { get; set; }
+    
+    /// <summary>
+    /// محصول
+    /// </summary>
+    public virtual DiscountProduct DiscountProduct { get; set; } = null!;
+    
+    /// <summary>
+    /// عنوان تصویر
+    /// </summary>
+    public string? Title { get; set; }
+    
+    /// <summary>
+    /// متن جایگزین (Alt)
+    /// </summary>
+    public string? AltText { get; set; }
+    
+    /// <summary>
+    /// مسیر تصویر اصلی
+    /// </summary>
+    public string ImagePath { get; set; } = string.Empty;
+    
+    /// <summary>
+    /// مسیر تصویر کوچک
+    /// </summary>
+    public string? ThumbnailPath { get; set; }
+    
+    /// <summary>
+    /// ترتیب نمایش
+    /// </summary>
+    public int SortOrder { get; set; }
+    
+    /// <summary>
+    /// آیا فعال است؟
+    /// </summary>
+    public bool IsActive { get; set; } = true;
+}