Refactor Intelligence Toolbar (#14) and fix auth regression (#24)

This PR resolves the authentication regression issue where users encountered "Unauthorized" errors after logging out and back in. This regression was identified during the refactoring of the Intelligence Toolbar.

Fixes #14

### Changes:
- **WASM Client**: Added `AuthenticationHeaderHandler` to automatically attach Bearer tokens to `HttpClient` requests.
- **Server**: Configured Cookie authentication to return `401 Unauthorized` for `/api` requests instead of redirecting to the login page.
- **Project Configuration**: Added `Microsoft.Extensions.Http` to the WASM client project to support `IHttpClientFactory` and message handlers.

Verified with local build.

Reviewed-on: #24
Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Co-committed-by: Marek Jasiński <jasins.marek@gmail.com>

src/NexusReader.Web.New/Program.cs

@@ -96,6 +96,18 @@ builder.Services.ConfigureApplicationCookie(options =>
     options.Cookie.HttpOnly = true;
     options.ExpireTimeSpan = TimeSpan.FromDays(30);
     options.SlidingExpiration = true;
+    options.Events.OnRedirectToLogin = context =>
+    {
+        if (context.Request.Path.StartsWithSegments("/api"))
+        {
+            context.Response.StatusCode = 401;
+        }
+        else
+        {
+            context.Response.Redirect(context.RedirectUri);
+        }
+        return Task.CompletedTask;
+    };
 });
 
 builder.Services.Configure<IdentityOptions>(options =>