feat(client): add AuthRedirectHandler for global 401 redirect

Add HTTP message handler that intercepts 401 Unauthorized responses
and redirects to the login page with return URL preserved.

NEW/src/JdeScoping.Client/Http/AuthRedirectHandler.cs

@@ -0,0 +1,33 @@
+using System.Net;
+using Microsoft.AspNetCore.Components;
+
+namespace JdeScoping.Client.Http;
+
+/// <summary>
+/// HTTP message handler that intercepts 401 Unauthorized responses
+/// and redirects to the login page with return URL.
+/// </summary>
+public class AuthRedirectHandler : DelegatingHandler
+{
+    private readonly NavigationManager _navigationManager;
+
+    public AuthRedirectHandler(NavigationManager navigationManager)
+    {
+        _navigationManager = navigationManager;
+    }
+
+    protected override async Task<HttpResponseMessage> SendAsync(
+        HttpRequestMessage request,
+        CancellationToken cancellationToken)
+    {
+        var response = await base.SendAsync(request, cancellationToken);
+
+        if (response.StatusCode == HttpStatusCode.Unauthorized)
+        {
+            var returnUrl = Uri.EscapeDataString(_navigationManager.Uri);
+            _navigationManager.NavigateTo($"/login?returnUrl={returnUrl}", forceLoad: true);
+        }
+
+        return response;
+    }
+}