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/Components/Organisms/KnowledgeGraph.razor.css

@@ -98,3 +98,13 @@
     filter: drop-shadow(0 0 12px var(--nexus-neon));
     transition: all 0.3s ease;
 }
+
+::deep @keyframes neon-flash {
+    0% { filter: brightness(1) drop-shadow(0 0 0px var(--nexus-neon)); }
+    50% { filter: brightness(3) drop-shadow(0 0 30px var(--nexus-neon)); }
+    100% { filter: brightness(1) drop-shadow(0 0 0px var(--nexus-neon)); }
+}
+
+::deep .neon-flash-node {
+    animation: neon-flash 0.8s ease-out;
+}