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.UI.Shared/Components/Organisms/ReaderCanvas.razor

@@ -11,6 +11,8 @@
 @inject KnowledgeCoordinator Coordinator
 @inject IReaderInteractionService InteractionService
 @inject ISyncService SyncService
+@using Microsoft.AspNetCore.Components.Authorization
+@inject AuthenticationStateProvider AuthStateProvider
 
 <div class="reader-canvas @(ThemeService.IsLightMode ? "theme-light" : "theme-dark")">
     @if (ViewModel == null)
@@ -118,8 +120,19 @@
     {
         await Coordinator.OnBlockReachedAsync(blockId, content);
         
-        // Debounce sync update (simple version: every 5 seconds or on a timer)
-        await SyncService.UpdateProgressAsync(blockId);
+        if (ViewModel != null)
+        {
+            // Calculate progress: (CurrentChapter / TotalChapters) * 100 
+            // Simple approximation for now: chapter-based
+            double progress = ((double)(ViewModel.CurrentChapterIndex + 1) / ViewModel.TotalChapters) * 100;
+            
+            await SyncService.UpdateProgressAsync(
+                blockId, 
+                ViewModel.EbookId, 
+                progress, 
+                ViewModel.ChapterTitle,
+                ViewModel.CurrentChapterIndex);
+        }
     }
 
     private async Task HandleSyncProgressReceived(string blockId, DateTime timestamp)
@@ -180,7 +193,10 @@
         ViewModel = null;
         StatusMessage = "Fetching content...";
         
-        var result = await Mediator.Send(new GetReaderPageQuery(index));
+        var authState = await AuthStateProvider.GetAuthenticationStateAsync();
+        var userId = authState.User.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier)?.Value;
+
+        var result = await Mediator.Send(new GetReaderPageQuery(index, userId));
         if (result.IsSuccess)
         {
             ViewModel = result.Value;