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/NexusReader.UI.Shared.csproj

@@ -12,6 +12,7 @@
     <PackageReference Include="Microsoft.AspNetCore.Components.Authorization" Version="10.0.7" />
     <PackageReference Include="Microsoft.AspNetCore.Components.Web" Version="10.0.7" />
     <PackageReference Include="MediatR" Version="12.1.1" />
+    <PackageReference Include="Microsoft.AspNetCore.WebUtilities" Version="10.0.7" />
     <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.7" />
     <PackageReference Include="Microsoft.AspNetCore.SignalR.Client" Version="10.0.7" />
   </ItemGroup>