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.Maui/MauiProgram.cs

@@ -1,9 +1,13 @@
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
 using NexusReader.Application.Abstractions.Services;
 using NexusReader.Infrastructure.Mobile.Services;
 using NexusReader.UI.Shared.Services;
 using NexusReader.Application;
 using MediatR;
+using NexusReader.Maui.Infrastructure.Logging;
+using NexusReader.Maui.Infrastructure.Identity;
 
 namespace NexusReader.Maui;
 
@@ -14,16 +18,30 @@ public static class MauiProgram
 		try
 		{
 			var builder = MauiApp.CreateBuilder();
+
+			// Load embedded appsettings.json configuration
+			var assembly = typeof(App).Assembly;
+			using (var stream = assembly.GetManifestResourceStream("NexusReader.Maui.appsettings.json"))
+			{
+				if (stream != null)
+				{
+					((IConfigurationBuilder)builder.Configuration).AddJsonStream(stream);
+				}
+			}
+
 			builder
-				.UseMauiApp<App>();
+				.UseMauiApp<App>()
+				.RegisterLogging();
 
 			builder.Services.AddMauiBlazorWebView();
 
 #if DEBUG
 			builder.Services.AddBlazorWebViewDeveloperTools();
-			builder.Logging.AddDebug();
 #endif
 
+			// Interception bridge for JS/Blazor WebView logs
+			builder.Services.AddSingleton<BlazorLoggingBridge>();
+
 			// Minimal Infrastructure
 			builder.Services.AddSingleton<IPlatformService, MauiPlatformService>();
 			builder.Services.AddSingleton<INativeStorageService, MauiStorageService>();
@@ -34,8 +52,15 @@ public static class MauiProgram
 				sp.GetRequiredService<NexusAuthenticationStateProvider>());
 			builder.Services.AddAuthorizationCore();
 
-			// Basic Network
-			builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri("http://10.0.2.2:5000") });
+			// Basic Network with Secure Token Handler
+			builder.Services.AddTransient<MobileAuthenticationHeaderHandler>();
+			builder.Services.AddHttpClient("NexusAPI", client =>
+			{
+				var apiBaseUrl = builder.Configuration["ApiSettings:BaseUrl"] ?? "http://localhost:5000";
+				client.BaseAddress = new Uri(apiBaseUrl);
+			}).AddHttpMessageHandler<MobileAuthenticationHeaderHandler>();
+
+			builder.Services.AddScoped(sp => sp.GetRequiredService<IHttpClientFactory>().CreateClient("NexusAPI"));
 
 			// UI State
 			builder.Services.AddScoped<IThemeService, ThemeService>();