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.Application/Common/Interfaces/IApplicationDbContext.cs

@@ -51,6 +51,7 @@ public interface IApplicationDbContext
     DbSet<DiscountProduct> DiscountProducts { get; }
     DbSet<DiscountCategory> DiscountCategories { get; }
     DbSet<DiscountProductCategory> DiscountProductCategories { get; }
+    DbSet<DiscountProductImage> DiscountProductImages { get; }
     DbSet<DiscountShoppingCart> DiscountShoppingCarts { get; }
     DbSet<DiscountOrder> DiscountOrders { get; }
     DbSet<DiscountOrderDetail> DiscountOrderDetails { get; }