feat: smart product autocomplete for inventory dialogs

- DiscountProductsAutoComplete: new autocomplete component for discount
  products with search/debounce (mirrors ProductsAutoComplete pattern)
- AddStockDialog: replace manual product ID input with smart autocomplete
  - When 'regular product' selected → shows ProductsAutoComplete
  - When 'discount product' selected → shows DiscountProductsAutoComplete
  - Admin never has to type product IDs manually
  - Product type selector controls which autocomplete is shown
- Validates product selection before submit

src/BackOffice/Pages/AutoComplete/DiscountProductsAutoComplete.razor

@@ -0,0 +1,14 @@
+@using CMSMicroservice.Protobuf.Protos.DiscountProduct
+
+<MudAutocomplete T="DiscountProductDto"
+                 Label="@Label"
+                 Value="@_item"
+                 DebounceInterval="700"
+                 ValueChanged="@((e) => OnSelected(e))"
+                 ToStringFunc="@(e => e == null ? null : e.Title)"
+                 SearchFunc="@Search"
+                 Variant="Variant.Outlined"
+                 Clearable="true"
+                 ShowProgressIndicator="true"
+                 CoerceText="false"
+                 OnClearButtonClick="()=> OnSelected(null)" />

src/BackOffice/Pages/AutoComplete/DiscountProductsAutoComplete.razor.cs

@@ -0,0 +1,83 @@
+using CMSMicroservice.Protobuf.Protos.DiscountProduct;
+using Microsoft.AspNetCore.Components;
+
+namespace BackOffice.Pages.AutoComplete;
+
+public partial class DiscountProductsAutoComplete
+{
+    [Inject] public DiscountProductContract.DiscountProductContractClient DiscountProductService { get; set; } = default!;
+
+    [Parameter] public long? Value { get; set; }
+    [Parameter] public string? Label { get; set; } = "محصول تخفیفی";
+    [Parameter] public EventCallback<long?> ValueChanged { get; set; }
+
+    private List<DiscountProductDto> _items = new();
+    private DiscountProductDto? _item;
+
+    protected override async void OnParametersSet()
+    {
+        await base.OnParametersSetAsync();
+
+        if (Value.HasValue && Value.Value > 0 && (_item == null || _item.Id != Value.Value))
+        {
+            try
+            {
+                var getAll = await DiscountProductService.GetDiscountProductsAsync(new GetDiscountProductsRequest
+                {
+                    PageNumber = 1,
+                    PageSize = 50
+                });
+
+                if (getAll?.Models != null)
+                {
+                    _item = getAll.Models.FirstOrDefault(x => x.Id == Value.Value);
+                    StateHasChanged();
+                }
+            }
+            catch
+            {
+                // Silently handle
+            }
+        }
+    }
+
+    private async Task OnSelected(DiscountProductDto? model)
+    {
+        if (model == null)
+        {
+            _item = null;
+            await ValueChanged.InvokeAsync(null);
+        }
+        else
+        {
+            _item = model;
+            await ValueChanged.InvokeAsync(model.Id);
+        }
+    }
+
+    private async Task<IEnumerable<DiscountProductDto>> Search(string value, CancellationToken token)
+    {
+        var request = new GetDiscountProductsRequest
+        {
+            PageNumber = 1,
+            PageSize = 9
+        };
+
+        if (!string.IsNullOrWhiteSpace(value))
+        {
+            request.SearchQuery = value;
+        }
+
+        try
+        {
+            var getAll = await DiscountProductService.GetDiscountProductsAsync(request);
+            _items = getAll?.Models?.ToList() ?? new List<DiscountProductDto>();
+        }
+        catch
+        {
+            _items = new List<DiscountProductDto>();
+        }
+
+        return _items;
+    }
+}

src/BackOffice/Pages/Inventory/Components/AddStockDialog.razor

@@ -1,6 +1,7 @@
 @using CMSMicroservice.Protobuf.Protos.Inventory
 @using Google.Protobuf.WellKnownTypes
 @using InventoryProductType = CMSMicroservice.Protobuf.Protos.Inventory.ProductType
+@using BackOffice.Pages.AutoComplete
 
 <MudDialog>
     <DialogContent>
@@ -19,12 +20,16 @@
                         </MudSelect>
                     </MudItem>
                     <MudItem xs="12">
-                        <MudNumericField T="long" @bind-Value="_productId"
-                                         Label="شناسه محصول"
-                                         Variant="Variant.Outlined"
-                                         Required="true"
-                                         RequiredError="شناسه محصول الزامی است"
-                                         Min="1" />
+                        @if (_productType == InventoryProductType.RegularProduct)
+                        {
+                            <ProductsAutoComplete @bind-Value="_productId"
+                                                  Label="انتخاب محصول عادی" />
+                        }
+                        else
+                        {
+                            <DiscountProductsAutoComplete @bind-Value="_discountProductId"
+                                                          Label="انتخاب محصول تخفیفی" />
+                        }
                     </MudItem>
                 }
                 else
@@ -103,7 +108,8 @@
     private bool _isSubmitting;
 
     private InventoryProductType _productType = InventoryProductType.RegularProduct;
-    private long _productId;
+    private long? _productId;
+    private long? _discountProductId;
     private long? _warehouseId;
     private int _quantity = 1;
     private string _referenceNumber = string.Empty;
@@ -111,9 +117,12 @@
 
     protected override void OnInitialized()
     {
-        if (ProductIdParam.HasValue)
+        if (ProductIdParam.HasValue && ProductTypeParam.HasValue)
         {
-            _productId = ProductIdParam.Value;
+            if (ProductTypeParam.Value == InventoryProductType.DiscountProduct)
+                _discountProductId = ProductIdParam.Value;
+            else
+                _productId = ProductIdParam.Value;
         }
         if (ProductTypeParam.HasValue)
         {
@@ -144,9 +153,19 @@
         _isSubmitting = true;
         try
         {
+            var selectedProductId = ProductIdParam 
+                ?? (_productType == InventoryProductType.DiscountProduct ? _discountProductId : _productId);
+
+            if (!selectedProductId.HasValue || selectedProductId.Value <= 0)
+            {
+                Snackbar.Add("لطفاً یک محصول انتخاب کنید", Severity.Warning);
+                _isSubmitting = false;
+                return;
+            }
+
             var request = new AddStockRequest
             {
-                ProductId = ProductIdParam ?? _productId,
+                ProductId = selectedProductId.Value,
                 ProductType = ProductTypeParam ?? _productType,
                 Quantity = _quantity,
                 ReferenceNumber = _referenceNumber ?? string.Empty,