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.Infrastructure/RealTime/SyncHub.cs

@@ -2,6 +2,7 @@ using MediatR;
 using Microsoft.AspNetCore.SignalR;
 using Microsoft.AspNetCore.Authorization;
 using NexusReader.Application.Commands.Sync;
+using System.Security.Claims;
 
 namespace NexusReader.Infrastructure.RealTime;
 
@@ -15,12 +16,12 @@ public class SyncHub : Hub
         _mediator = mediator;
     }
 
-    public async Task UpdateProgress(string pageId)
+    public async Task UpdateProgress(string pageId, Guid ebookId, double progress, string? chapterTitle, int chapterIndex)
     {
-        var userId = Context.UserIdentifier;
-        if (!string.IsNullOrEmpty(userId))
+        var userId = Context.User?.FindFirst(ClaimTypes.NameIdentifier)?.Value;
+        if (userId != null)
         {
-            await _mediator.Send(new UpdateReadingProgressCommand(pageId, userId, Context.ConnectionId));
+            await _mediator.Send(new UpdateReadingProgressCommand(pageId, userId, ebookId, progress, chapterTitle, chapterIndex, Context.ConnectionId));
         }
     }