feat(client): migrate ItemNumberFilterPanel to API clients

Update ItemNumberFilterPanel.razor to use ILookupApiClient and IFileApiClient
instead of legacy ILookupService and IFileService interfaces. All methods now
use the result.Switch() pattern for proper ApiResult error handling.

NEW/src/JdeScoping.Client/Components/FilterPanels/ItemNumberFilterPanel.razor

@@ -1,6 +1,7 @@
 @* Item number filter panel with autocomplete and grid *@
-@inject ILookupService LookupService
+@using JdeScoping.Core.ApiContracts
-@inject IFileService FileService
+@inject ILookupApiClient LookupApi
+@inject IFileApiClient FileApi
 @inject DialogService DialogService
 @inject NotificationService NotificationService
 
@@ -78,7 +79,15 @@
     {
         if (!string.IsNullOrEmpty(args.Filter) && args.Filter.Length >= 3)
         {
-            _searchResults = await LookupService.FindItemsAsync(args.Filter);
+            var result = await LookupApi.FindItemsAsync(args.Filter);
+            result.Switch(
+                items => { _searchResults = items.ToList(); },
+                _ => { _searchResults = []; },
+                _ => { _searchResults = []; },
+                _ => { _searchResults = []; },
+                _ => { _searchResults = []; },
+                _ => { _searchResults = []; }
+            );
         }
         else
         {
@@ -117,7 +126,15 @@
 
     private async Task DownloadTemplateAsync()
     {
-        await FileService.DownloadTemplateAsync("items", Items);
+        var result = await FileApi.DownloadItemsTemplateAsync(Items.AsReadOnly());
+        result.Switch(
+            bytes => { _ = JSRuntime.InvokeVoidAsync("downloadFile", "items_template.xlsx", bytes); },
+            _ => { NotificationService.Notify(NotificationSeverity.Error, "Error", "Template not found."); },
+            validation => { NotificationService.Notify(NotificationSeverity.Error, "Error", string.Join("; ", validation.FieldErrors.SelectMany(e => e.Value))); },
+            _ => { NotificationService.Notify(NotificationSeverity.Error, "Error", "Session expired."); },
+            _ => { NotificationService.Notify(NotificationSeverity.Error, "Error", "Access denied."); },
+            error => { NotificationService.Notify(NotificationSeverity.Error, "Error", error.Message); }
+        );
     }
 
     private async Task TriggerFileInput()
@@ -132,20 +149,23 @@
         _isUploading = true;
         try
         {
-            using var stream = e.File.OpenReadStream(maxAllowedSize: 10 * 1024 * 1024); // 10MB max
+            using var stream = e.File.OpenReadStream(maxAllowedSize: 10 * 1024 * 1024);
-            var result = await FileService.UploadAsync<ItemViewModel>("items", stream, e.File.Name);
+            var result = await FileApi.UploadItemsAsync(stream, e.File.Name);
 
-            if (result.WasSuccessful)
+            result.Switch(
-            {
+                items =>
-                Items.Clear();
+                {
-                Items.AddRange(result.Data);
+                    Items.Clear();
-                await ItemsChanged.InvokeAsync(Items);
+                    Items.AddRange(items);
-                NotificationService.Notify(NotificationSeverity.Success, "Upload Complete", $"Loaded {result.Data.Count} items.");
+                    _ = ItemsChanged.InvokeAsync(Items);
-            }
+                    NotificationService.Notify(NotificationSeverity.Success, "Upload Complete", $"Loaded {items.Count} items.");
-            else
+                },
-            {
+                _ => { NotificationService.Notify(NotificationSeverity.Error, "Error", "Upload endpoint not found."); },
-                NotificationService.Notify(NotificationSeverity.Error, "Upload Failed", result.ErrorMessage);
+                validation => { NotificationService.Notify(NotificationSeverity.Error, "Upload Failed", string.Join("; ", validation.FieldErrors.SelectMany(e => e.Value))); },
-            }
+                _ => { NotificationService.Notify(NotificationSeverity.Error, "Error", "Session expired."); },
+                _ => { NotificationService.Notify(NotificationSeverity.Error, "Error", "Access denied."); },
+                error => { NotificationService.Notify(NotificationSeverity.Error, "Upload Failed", error.Message); }
+            );
         }
         catch (Exception ex)
         {