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.Web.Client/Program.cs

@@ -4,6 +4,9 @@ using NexusReader.Application.Abstractions.Services;
 using NexusReader.Web.Client.Services;
 using NexusReader.UI.Shared.Services;
 using NexusReader.Application;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.AI;
+using NexusReader.Data.Persistence;
 
 
 var builder = WebAssemblyHostBuilder.CreateDefault(args);
@@ -32,7 +35,24 @@ builder.Services.AddCascadingAuthenticationState();
 builder.Services.AddScoped<IKnowledgeService, WasmKnowledgeService>();
 builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });
 
+// Dummy registrations for server-only handlers to satisfy DI validation
+builder.Services.AddSingleton<IDbContextFactory<AppDbContext>>(new ThrowingDbContextFactory());
+builder.Services.AddSingleton<IEmbeddingGenerator<string, Embedding<float>>>(new ThrowingEmbeddingGenerator());
+
 builder.Services.AddApplication();
 builder.Services.AddScoped<IEpubService, WasmEpubService>();
 
 await builder.Build().RunAsync();
+
+public class ThrowingDbContextFactory : IDbContextFactory<AppDbContext>
+{
+    public AppDbContext CreateDbContext() => throw new NotSupportedException("DbContext cannot be used in WASM client.");
+}
+
+public class ThrowingEmbeddingGenerator : IEmbeddingGenerator<string, Embedding<float>>
+{
+    public void Dispose() { }
+    public Task<GeneratedEmbeddings<Embedding<float>>> GenerateAsync(IEnumerable<string> values, EmbeddingGenerationOptions? options = null, CancellationToken cancellationToken = default) 
+        => throw new NotSupportedException("Embedding generation cannot be used in WASM client.");
+    public object? GetService(Type serviceType, object? serviceKey = null) => null;
+}