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/ReaderCanvas.razor.css

@@ -1,16 +1,47 @@
 .reader-canvas {
-    max-width: 800px;
-    margin: 0 auto;
-    padding: 2rem 1rem;
+    width: 100%;
+    height: 100%;
+    overflow-y: auto;
+    overflow-x: hidden;
+    padding: 2rem 0;
     transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
     position: relative;
+    
+    /* Dedicated Scrollbar Styling */
+    scrollbar-width: thin;
+    scrollbar-color: rgba(0, 255, 153, 0.2) transparent;
+}
+
+.reader-canvas::-webkit-scrollbar {
+    width: 6px;
+}
+
+.reader-canvas::-webkit-scrollbar-track {
+    background: transparent;
+}
+
+.reader-canvas::-webkit-scrollbar-thumb {
+    background-color: rgba(0, 255, 153, 0.2);
+    border-radius: 20px;
+    border: 3px solid transparent;
+}
+
+.reader-canvas:hover::-webkit-scrollbar-thumb {
+    background-color: rgba(0, 255, 153, 0.5);
+}
+
+.reader-canvas.theme-light {
+    background-color: #F9F9F9; /* Paper-white requirement */
 }
 
 .reader-flow-container {
+    max-width: 800px;
+    margin: 0 auto;
     display: flex;
     flex-direction: column;
     gap: 1.5rem;
     position: relative;
+    padding: 0 1.5rem 15rem 1.5rem; /* Large padding-bottom for reachability */
 }
 
 .block-wrapper {
@@ -20,6 +51,68 @@
     border: 1px solid transparent;
 }
 
+/* Typographic refinement for TextSegmentBlock */
+::deep .nexus-ebook {
+    font-family: 'Merriweather', serif !important;
+    line-height: 1.65 !important;
+    letter-spacing: -0.01em !important;
+    font-size: 1.15rem;
+    font-weight: 300;
+}
+
+.theme-light ::deep .nexus-ebook {
+    color: #1a1a1a;
+}
+
+/* Technical Code Block Container */
+::deep .nexus-ebook pre {
+    background-color: #2d2d2d; /* Dark theme for code for better contrast */
+    color: #e0e0e0;
+    padding: 1.25rem;
+    border-radius: 8px;
+    margin: 2rem 0;
+    overflow-x: auto;
+    box-shadow: inset 0 2px 4px rgba(0,0,0,0.1);
+    border-left: 4px solid var(--nexus-neon); /* Nexus neon accent */
+    
+    /* Dedicated Scrollbar for Code */
+    scrollbar-width: thin;
+    scrollbar-color: rgba(0, 255, 153, 0.3) transparent;
+}
+
+::deep .nexus-ebook pre::-webkit-scrollbar {
+    height: 4px;
+}
+
+::deep .nexus-ebook pre::-webkit-scrollbar-thumb {
+    background: rgba(0, 255, 153, 0.3);
+    border-radius: 10px;
+}
+
+/* Monospace Typography Contrast */
+::deep .nexus-ebook code {
+    font-family: 'JetBrains Mono', 'Cascadia Code', 'Consolas', monospace !important;
+    font-variant-ligatures: contextual;
+    line-height: 1.5;
+    tab-size: 4;
+    font-size: 0.9rem;
+}
+
+/* Inline Code Highlight */
+::deep .nexus-ebook p code {
+    background-color: rgba(0, 0, 0, 0.05);
+    color: #d63384; /* Classic differentiator for inline code */
+    padding: 0.2rem 0.4rem;
+    border-radius: 4px;
+    font-size: 0.9em;
+    border: none;
+}
+
+.theme-dark ::deep .nexus-ebook p code {
+    background-color: rgba(255, 255, 255, 0.1);
+    color: #ff79c6;
+}
+
 .block-wrapper.highlighted {
     background: rgba(0, 243, 255, 0.08);
     box-shadow: 0 0 20px rgba(0, 243, 255, 0.15);