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/Handlers/UpdateReadingProgressCommandHandler.cs

@@ -35,6 +35,16 @@ public class UpdateReadingProgressCommandHandler : IRequestHandler<UpdateReading
         user.LastReadPageId = request.PageId;
         user.LastReadAt = now;
 
+        // Update specific Ebook progress
+        var ebook = await context.Ebooks.FirstOrDefaultAsync(e => e.Id == request.EbookId, cancellationToken);
+        if (ebook != null)
+        {
+            ebook.Progress = request.Progress;
+            ebook.LastChapter = request.ChapterTitle;
+            ebook.LastChapterIndex = request.ChapterIndex;
+            ebook.LastReadDate = now;
+        }
+
         await context.SaveChangesAsync(cancellationToken);
 
         // Broadcast to other devices