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/Pages/Home.razor

@@ -1,10 +1,13 @@
-@page "/"
+@page "/reader"
+@layout ReaderLayout
 @attribute [Authorize]
 @using NexusReader.UI.Shared.Services
 @implements IAsyncDisposable
 @inject IQuizStateService QuizState
 @inject IFocusModeService FocusMode
 @inject IJSRuntime JS
+@inject NavigationManager NavManager
+@inject IReaderNavigationService NavService
 <PageTitle>Nexus E-Reader</PageTitle>
 
 <div class="home-reader-container">
@@ -25,6 +28,16 @@
         QuizState.OnQuizRequested += HandleQuizRequestedAsync;
         FocusMode.OnFocusModeChanged += HandleUpdate;
         await FocusMode.InitializeAsync();
+
+        // Handle deep-linking to a specific chapter
+        var uri = NavManager.ToAbsoluteUri(NavManager.Uri);
+        if (Microsoft.AspNetCore.WebUtilities.QueryHelpers.ParseQuery(uri.Query).TryGetValue("chapter", out var chapterValue))
+        {
+            if (int.TryParse(chapterValue, out var chapterIndex))
+            {
+                await NavService.GoToChapter(chapterIndex);
+            }
+        }
     }
 
     protected override async Task OnAfterRenderAsync(bool firstRender)