feat(ui): Hub Navigation, Profile Dashboard and Auth Stability Fixes (#31)

This PR implements the Hub Navigation system and the Profile Dashboard, while resolving critical session synchronization issues.

### Key Changes
- **Hub Navigation**: Introduced `MainHubLayout` with a premium glassmorphism sidebar, providing access to Dashboard, Library, Concepts Map, and Profile.
- **Profile Dashboard**: Implemented a high-fidelity Profile page (#27) with learning metrics, AI token usage tracking, and system rank visualization.
- **Stability Fixes**:
    - Resolved an infinite network loop on the `/profile` page by implementing request deduplication and in-memory caching in `IdentityService`.
    - Added environment-aware guards to prevent illegal JavaScript interop calls during server-side prerendering.
    - Implemented automatic session invalidation on `401 Unauthorized` responses to handle stale authentication states gracefully.
- **Reader Integration**: Added a "Return to Dashboard" option in the reader toolbar (#26).

Closes #26
Closes #27

Reviewed-on: #31
Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Co-committed-by: Marek Jasiński <jasins.marek@gmail.com>

src/NexusReader.Web.Client/Handlers/AuthenticationHeaderHandler.cs

@@ -1,4 +1,5 @@
 using System.Net.Http.Headers;
+using Microsoft.AspNetCore.Components.WebAssembly.Http;
 using NexusReader.Application.Abstractions.Services;
 
 namespace NexusReader.Web.Client.Handlers;
@@ -15,6 +16,9 @@ public class AuthenticationHeaderHandler : DelegatingHandler
 
     protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
     {
+        // Ensure cookies are sent (needed for InteractiveAuto SSR synchronization)
+        request.SetBrowserRequestCredentials(BrowserRequestCredentials.Include);
+
         var tokenResult = await _storageService.GetSecureString(TokenKey);
         
         if (tokenResult.IsSuccess && !string.IsNullOrEmpty(tokenResult.Value))