Refactor CartService to use async methods for cart operations and integrate gRPC for backend synchronization

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

@@ -14,14 +14,14 @@ public partial class Cart : ComponentBase, IDisposable
         CartService.OnChange += StateHasChanged;
     }
 
-    private void ChangeQty(long productId, int value)
+    private async Task ChangeQty(long productId, int value)
     {
-        CartService.UpdateQuantity(productId, value);
+        await CartService.UpdateQuantity(productId, value);
     }
 
-    private void Remove(long productId)
+    private async Task Remove(long productId)
     {
-        CartService.Remove(productId);
+        await CartService.Remove(productId);
     }
 
     private void ProceedCheckout()

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

@@ -72,7 +72,7 @@ public partial class CheckoutSummary : ComponentBase
         };
 
         var id = await OrderService.CreateOrderAsync(order);
-        Cart.Clear();
+        await Cart.Clear();
         Snackbar.Add("سفارش با موفقیت ثبت شد.", Severity.Success);
         Navigation.NavigateTo($"{RouteConstants.Store.OrderDetail}{id}");
     }

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

@@ -21,10 +21,10 @@ public partial class ProductDetail : ComponentBase
         _loading = false;
     }
 
-    private void AddToCart()
+    private async Task AddToCart()
     {
         if (_product is null) return;
-        Cart.Add(_product, _qty);
+        await Cart.Add(_product, _qty);
     }
 
     private static string FormatPrice(long price) => string.Format("{0:N0} تومان", price);

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

@@ -31,9 +31,9 @@ public partial class Products : ComponentBase, IDisposable
         await Load();
     }
 
-    private void AddToCart(Product p)
+    private async Task AddToCart(Product p)
     {
-        Cart.Add(p, 1);
+        await Cart.Add(p, 1);
     }
 
     private static string FormatPrice(long price) => string.Format("{0:N0} تومان", price);