Add validators and services for Product Galleries and Product Tags

- Implemented Create, Delete, Get, and Update validators for Product Galleries.
- Added Create, Delete, Get, and Update validators for Product Tags.
- Created service classes for handling Discount Categories, Discount Orders, Discount Products, Discount Shopping Cart, Product Categories, Product Galleries, and Product Tags.
- Each service class integrates with CQRS for command and query handling.
- Established mapping profiles for Product Galleries.

src/CMSMicroservice.Domain/Entities/Order/OrderVAT.cs

@@ -0,0 +1,55 @@
+using CMSMicroservice.Domain.Common;
+
+namespace CMSMicroservice.Domain.Entities.Order;
+
+/// <summary>
+/// مالیات بر ارزش افزوده (VAT) سفارش
+/// محاسبه و ثبت مالیات ۹٪ برای سفارشات
+/// </summary>
+public class OrderVAT : BaseAuditableEntity
+{
+    /// <summary>
+    /// شناسه سفارش
+    /// </summary>
+    public long OrderId { get; set; }
+
+    /// <summary>
+    /// UserOrder Navigation Property
+    /// </summary>
+    public virtual UserOrder Order { get; set; } = null!;
+
+    /// <summary>
+    /// نرخ مالیات (معمولاً ۹٪ = 0.09)
+    /// </summary>
+    public decimal VATRate { get; set; }
+
+    /// <summary>
+    /// مبلغ پایه (قبل از مالیات)
+    /// </summary>
+    public long BaseAmount { get; set; }
+
+    /// <summary>
+    /// مبلغ مالیات محاسبه شده
+    /// </summary>
+    public long VATAmount { get; set; }
+
+    /// <summary>
+    /// مبلغ کل (پایه + مالیات)
+    /// </summary>
+    public long TotalAmount { get; set; }
+
+    /// <summary>
+    /// آیا مالیات پرداخت شده است
+    /// </summary>
+    public bool IsPaid { get; set; }
+
+    /// <summary>
+    /// تاریخ پرداخت مالیات
+    /// </summary>
+    public DateTime? PaidAt { get; set; }
+
+    /// <summary>
+    /// یادداشت (اختیاری)
+    /// </summary>
+    public string? Note { get; set; }
+}