feat(ui/arch): Optimize Graph Dynamics, Immersive Reader, and Core Stability (#19)

This PR introduces a major optimization of graph dynamics, immersive reading experience, and architectural stabilization.

### 🚀 Key Improvements

- **Knowledge Graph (Fix #16)**:
  - Implemented smooth D3.js transitions using the General Update Pattern.
  - Added "Neon Flash" entry animations and dynamic node dimming for better focus.
- **Immersive Reader (Fix #12)**:
  - Standardized centered layout (`max-width: 800px`) with **Merriweather** typography.
  - Optimized line-height and letter-spacing for premium readability.
- **Technical Code Blocks (Fix #20)**:
  - High-contrast dark containers for code snippets.
  - **JetBrains Mono** integration and neon-accented scrollbars.
- **Architectural Stabilization**:
  - Enforced a strict **'no async void'** policy in UI services using `Func<Task>`.
  - Resolved WASM runtime DI errors by implementing dummy service proxies for server-side dependencies.
  - Replaced generic 'Not Found' message with a branded Nexus preloader.

Fixes #7, Fixes #12, Fixes #16, Fixes #20.

Reviewed-on: #19
Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Co-committed-by: Marek Jasiński <jasins.marek@gmail.com>

src/NexusReader.UI.Shared/Services/IQuizStateService.cs

@@ -9,11 +9,11 @@ public interface IQuizStateService
     bool IsHydrating { get; }
     bool HasNewQuiz { get; }
     
-    event Action<string>? OnQuizRequested;
-    event Action? OnQuizUpdated;
+    event Func<string, Task>? OnQuizRequested;
+    event Func<Task>? OnQuizUpdated;
     
-    void RequestQuiz(string blockId);
-    void SetQuiz(string? blockId, QuizDto quiz);
-    void SetHydrating(bool hydrating);
-    void MarkQuizAsSeen();
+    Task RequestQuiz(string blockId);
+    Task SetQuiz(string? blockId, QuizDto? quiz);
+    Task SetHydrating(bool hydrating);
+    Task MarkQuizAsSeen();
 }