feat(search/rag): implement NexusSearchBox, dynamic Qdrant collection auto-provisioning, batch vector ingestion, mobile Serilog logging, and resolve 401 auth handler error (#51)

Resolves #52

This Pull Request introduces the **NexusSearchBox** search feature with premium unified styling, implements a robust **dynamic Qdrant collection auto-provisioning and batch-vector ingestion pipeline**, integrates a unified **Serilog logging infrastructure** for the Blazor Hybrid environment (MAUI), and resolves the **401 Unauthorized API header propagation error** inside mobile builds.

### 🚀 Key Implementations

#### 1. Premium `NexusSearchBox` & Semantic Search UI
* **NexusSearchBox Component:** Created an elegant search-as-you-type search box with smooth key navigation, quick-clearing, and seamless dynamic styling.
* **Unified Aesthetics:** Refactored the search box isolated styling to align perfectly with the dashboard's design system using glassmorphism, `--nexus-neon` token gradients, and smooth pulse/fade animations.
* **Semantic Search Integration:** Integrated semantic search query dispatching (`SearchLibrarySemanticallyQuery`) and wired up navigation seamlessly through the updated `ReaderNavigationService`.
* **Tests Hardening:** Added/adapted query assertions in `QueryTests.cs` to guarantee safe parameterization and error boundary mapping.

#### 2. Qdrant Collection Provisioning & Vector Ingestion
* **Dynamic Auto-Provisioning:** Implemented dynamic checking and lazy-creation of the `knowledge_units` collection using 768 dimensions and Cosine distance.
* **High-Performance Ingestion:** Optimized `ProcessKnowledgeUnitsAsync` with high-performance batch embedding generation using `_embeddingGenerator` and deterministic MD5 GUIDs for stable, duplicate-free upsertion.
* **Database Cache Clear Sync:** Integrated Qdrant collection deletion in `ClearCacheAsync` to ensure absolute consistency between the PostgreSQL database cache and vector database indices.

#### 3. Cross-Platform MAUI Logging (Serilog Infrastructure)
* **Serilog Integration:** Configured cross-platform Serilog routing in `SerilogConfiguration.cs`, streaming diagnostic logs safely across native platforms and the Blazor Webview container.
* **Interop Bridge:** Built `BlazorLoggingBridge.cs` to capture web console messages and pipe them directly to the native host logger.
* **Demo Interface:** Added an interactive `SerilogDemo.razor` sandbox under Pages.

#### 4. Resolving 401 Load Errors (Authentication Handler Flow)
* **Authentication Header Handler:** Implemented the `MobileAuthenticationHeaderHandler` to correctly extract, validate, and inject bearer JWT tokens into outbound API requests.
* **Configuration-based API Host:** Structured standard API URI routing to use clean configuration bindings in `appsettings.json`.

---

### 🧪 Verification & Build Status
* Run `dotnet build` from the solution root: Successfully compiled the full multi-targeted solution (`Liczba błędów: 0`).
* All unit and integration tests successfully executed and verified (`dotnet test`).

---------

Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Co-authored-by: Marek Jaisński <jasins.marek@gmail.com>
Reviewed-on: #51
Co-authored-by: Antigravity <antigravity@google.com>
Co-committed-by: Antigravity <antigravity@google.com>

src/NexusReader.Web.Client/Program.cs

@@ -50,7 +50,9 @@ builder.Services.AddSingleton<IDbContextFactory<AppDbContext>>(new ThrowingDbCon
 builder.Services.AddSingleton<IEmbeddingGenerator<string, Embedding<float>>>(new ThrowingEmbeddingGenerator());
 builder.Services.AddSingleton<IBookStorageService>(new ThrowingBookStorageService());
 builder.Services.AddSingleton<IEbookRepository>(new ThrowingEbookRepository());
+builder.Services.AddSingleton<IQuizResultRepository>(new ThrowingQuizResultRepository());
 builder.Services.AddSingleton<ISyncBroadcaster>(new ThrowingSyncBroadcaster());
+builder.Services.AddSingleton<IEpubExtractor>(new ThrowingEpubExtractor());
 
 builder.Services.AddApplication();
 builder.Services.AddScoped<IEpubReader, WasmEpubReader>();
@@ -88,6 +90,16 @@ public class ThrowingEbookRepository : IEbookRepository
     public Task<Author?> FindAuthorByNameAsync(string name, CancellationToken cancellationToken = default) => throw new NotSupportedException(ErrorMessage);
     public void AddAuthor(Author author) => throw new NotSupportedException(ErrorMessage);
     public void AddEbook(Ebook ebook) => throw new NotSupportedException(ErrorMessage);
+    public Task<Ebook?> FindByIdAsync(Guid id, CancellationToken cancellationToken = default) => throw new NotSupportedException(ErrorMessage);
+    public Task<int> SaveChangesAsync(CancellationToken cancellationToken = default) => throw new NotSupportedException(ErrorMessage);
+}
+
+public class ThrowingQuizResultRepository : IQuizResultRepository
+{
+    private const string ErrorMessage = "QuizResult repository operations are not supported in the WASM client. Use the API endpoint for data access.";
+
+    public Task<NexusUser?> FindUserByIdAsync(string userId, CancellationToken cancellationToken = default) => throw new NotSupportedException(ErrorMessage);
+    public void AddQuizResult(QuizResult quizResult) => throw new NotSupportedException(ErrorMessage);
     public Task<int> SaveChangesAsync(CancellationToken cancellationToken = default) => throw new NotSupportedException(ErrorMessage);
 }
 
@@ -99,3 +111,9 @@ public class ThrowingSyncBroadcaster : ISyncBroadcaster
     public Task BroadcastIngestionProgressAsync(string userId, string message, double progress, CancellationToken cancellationToken = default)
         => throw new NotSupportedException("Real-time broadcasting can only be performed by the server.");
 }
+
+public class ThrowingEpubExtractor : IEpubExtractor
+{
+    public Task<FluentResults.Result<List<string>>> ExtractChaptersTextAsync(string relativePath, CancellationToken cancellationToken = default)
+        => throw new NotSupportedException("EPUB text extraction is not supported in the WASM client.");
+}