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/Pages/Home.razor

@@ -22,8 +22,8 @@
 
     protected override async Task OnInitializedAsync()
     {
-        QuizState.OnQuizRequested += HandleQuizRequested;
-        FocusMode.OnFocusModeChanged += StateHasChanged;
+        QuizState.OnQuizRequested += HandleQuizRequestedAsync;
+        FocusMode.OnFocusModeChanged += HandleUpdate;
         await FocusMode.InitializeAsync();
     }
 
@@ -54,16 +54,18 @@
         }
     }
 
-    private void HandleQuizRequested(string blockId)
+    private async Task HandleQuizRequestedAsync(string blockId)
     {
         _activeQuizBlockId = blockId;
-        StateHasChanged();
+        await InvokeAsync(StateHasChanged);
     }
 
+    private Task HandleUpdate() => InvokeAsync(StateHasChanged);
+
     public async ValueTask DisposeAsync()
     {
-        QuizState.OnQuizRequested -= HandleQuizRequested;
-        FocusMode.OnFocusModeChanged -= StateHasChanged;
+        QuizState.OnQuizRequested -= HandleQuizRequestedAsync;
+        FocusMode.OnFocusModeChanged -= HandleUpdate;
         
         if (_interopModule != null && _keydownHandler != null)
         {

src/NexusReader.UI.Shared/Pages/Home.razor.css

@@ -1,8 +1,8 @@
 .home-reader-container {
     width: 100%;
+    height: 100%;
     max-width: 800px;
     margin: 0 auto;
-    padding: 2rem;
     transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
 }
 

src/NexusReader.UI.Shared/Pages/NotFound.razor

@@ -1,5 +1,10 @@
-@page "/not-found"
-@layout MainLayout
-
-<h3>Not Found</h3>
-<p>Sorry, the content you are looking for does not exist.</p>
+@page "/not-found"
+@layout Layout.MainLayout
+
+<div class="not-found-preloader">
+    <div class="preloader-robot">
+        <NexusIcon Name="robot" Size="64" class="neon-pulse" />
+        <div class="scan-line"></div>
+    </div>
+    <NexusTypography Variant="NexusTypography.TypographyVariant.UI">Synchronizowanie przestrzeni Nexus...</NexusTypography>
+</div>

src/NexusReader.UI.Shared/Pages/NotFound.razor.css

@@ -0,0 +1,42 @@
+.not-found-preloader {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    height: 60vh;
+    gap: 2rem;
+}
+
+.preloader-robot {
+    position: relative;
+    padding: 1rem;
+}
+
+.scan-line {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 2px;
+    background: var(--nexus-neon);
+    box-shadow: 0 0 10px var(--nexus-neon);
+    animation: scan 2s linear infinite;
+}
+
+@keyframes scan {
+    0% { top: 0; }
+    50% { top: 100%; }
+    100% { top: 0; }
+}
+
+.neon-pulse {
+    color: var(--nexus-neon);
+    filter: drop-shadow(0 0 5px var(--nexus-neon));
+    animation: pulse 2s infinite;
+}
+
+@keyframes pulse {
+    0% { transform: scale(1); opacity: 1; }
+    50% { transform: scale(1.1); opacity: 0.8; }
+    100% { transform: scale(1); opacity: 1; }
+}