feat: implement VAT management service and integrate VAT calculations across components

src/FrontOffice.Main/Pages/Store/ProductDetail.razor.cs

@@ -11,6 +11,7 @@ public partial class ProductDetail : ComponentBase, IDisposable
 {
     [Inject] private ProductService ProductService { get; set; } = default!;
     [Inject] private CartService Cart { get; set; } = default!;
+    [Inject] private VATService VAT { get; set; } = default!;
 
     [Parameter] public long id { get; set; }
 
@@ -18,12 +19,18 @@ public partial class ProductDetail : ComponentBase, IDisposable
     private bool _loading;
     private int _qty = 1;
     private const int MinQty = 1;
-    private const int MaxQty = 20;
+    
+    // حداکثر تعداد قابل خرید بر اساس موجودی انبار
+    private int MaxQty => _product?.RemainingCount > 0 ? _product.RemainingCount : 0;
+    
+    // آیا محصول موجود است
+    private bool IsInStock => _product is not null && _product.RemainingCount > 0;
+    
     private IReadOnlyList<ProductGalleryImage> _galleryItems = Array.Empty<ProductGalleryImage>();
     private IReadOnlyList<ProductCategoryPathInfo> _categoryPaths = Array.Empty<ProductCategoryPathInfo>();
     private ProductGalleryImage? _selectedGalleryImage;
     private readonly List<BreadcrumbItem> _breadcrumbItems = new();
-    private long TotalPrice => (_product?.Price ?? 0) * _qty;
+    private long TotalPrice => VAT.AddVAT((_product?.Price ?? 0) * _qty);
     private bool HasDiscount => _product is { Discount: > 0 and < 100 };
 
     private long? OriginalPrice => HasDiscount && _product is not null
@@ -44,8 +51,13 @@ public partial class ProductDetail : ComponentBase, IDisposable
 
     protected override async Task OnInitializedAsync()
     {
+        // لود سبد خرید (فقط اگر کاربر لاگین کرده باشد)
+        await Cart.EnsureInitializedAsync();
         Cart.OnChange += HandleCartChanged;
         
+        // بارگذاری نرخ VAT
+        await VAT.LoadAsync();
+        
         _loading = true;
         _product = await ProductService.GetByIdAsync(id);
         _loading = false;
@@ -127,7 +139,9 @@ public partial class ProductDetail : ComponentBase, IDisposable
         Cart.OnChange -= HandleCartChanged;
     }
 
-    private static string FormatPrice(long price) => string.Format("{0:N0} تومان", price);
+    private string FormatPrice(long price) => $"{VAT.AddVAT(price):N0} تومان";
+    
+    private string FormatPriceWithoutVAT(long price) => $"{price:N0} تومان";
 
     private static IReadOnlyList<ProductGalleryImage> BuildGalleryItems(Product product)
     {