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>

tests/NexusReader.Application.Tests/Queries/QueryTests.cs

@@ -116,11 +116,8 @@ public class QueryTests : IDisposable
     public async Task SearchLibrarySemanticallyQuery_WithEmptyQueryText_ReturnsFailure()
     {
         // Arrange
-        var handler = new SearchLibrarySemanticallyQueryHandler(
-            _embeddingGeneratorMock.Object,
-            _dbContextFactoryMock.Object,
-            _pipelineProviderMock.Object,
-            _mapperMock.Object);
+        var knowledgeServiceMock = new Mock<IKnowledgeService>();
+        var handler = new SearchLibrarySemanticallyQueryHandler(knowledgeServiceMock.Object);
         var query = new SearchLibrarySemanticallyQuery("", "tenant-123");
 
         // Act
@@ -132,39 +129,38 @@ public class QueryTests : IDisposable
     }
 
     [Fact]
-    public async Task SearchLibrarySemanticallyQuery_WithValidQuery_GeneratesEmbeddingAndQueriesDatabase()
+    public async Task SearchLibrarySemanticallyQuery_WithValidQuery_CallsKnowledgeService()
     {
         // Arrange
         var queryText = "test query";
         var tenantId = "tenant-123";
+        var expectedResponse = new List<SemanticSearchResultDto>
+        {
+            new SemanticSearchResultDto
+            {
+                Snippet = "Matched content",
+                RelevanceScore = 0.95f,
+                SourceBookTitle = "Test Book"
+            }
+        };
 
-        var mockEmbedding = new Embedding<float>(new float[768]);
-        var mockResponse = new GeneratedEmbeddings<Embedding<float>>(new[] { mockEmbedding });
-        _embeddingGeneratorMock.Setup(g => g.GenerateAsync(
-            It.Is<IEnumerable<string>>(s => s.Contains(queryText)),
-            It.IsAny<EmbeddingGenerationOptions>(),
-            It.IsAny<CancellationToken>()))
-            .ReturnsAsync(mockResponse);
-
-        var handler = new SearchLibrarySemanticallyQueryHandler(
-            _embeddingGeneratorMock.Object,
-            _dbContextFactoryMock.Object,
-            _pipelineProviderMock.Object,
-            _mapperMock.Object);
+        var knowledgeServiceMock = new Mock<IKnowledgeService>();
+        knowledgeServiceMock.Setup(s => s.SearchLibrarySemanticallyAsync(queryText, tenantId, 5, It.IsAny<CancellationToken>()))
+            .ReturnsAsync(Result.Ok(expectedResponse));
 
+        var handler = new SearchLibrarySemanticallyQueryHandler(knowledgeServiceMock.Object);
         var query = new SearchLibrarySemanticallyQuery(queryText, tenantId);
 
         // Act
-        Func<Task> act = async () => await handler.Handle(query, CancellationToken.None);
+        var result = await handler.Handle(query, CancellationToken.None);
 
-        // Assert (SQLite provider will throw an execution/translation exception since CosineDistance is not supported,
-        // which confirms that the query built successfully and attempted execution!)
-        await act.Should().ThrowAsync<Exception>();
+        // Assert
+        result.IsSuccess.Should().BeTrue();
+        result.Value.Should().HaveCount(1);
+        result.Value.First().Snippet.Should().Be("Matched content");
+        result.Value.First().SourceBookTitle.Should().Be("Test Book");
 
-        _embeddingGeneratorMock.Verify(g => g.GenerateAsync(
-            It.Is<IEnumerable<string>>(s => s.Contains(queryText)),
-            It.IsAny<EmbeddingGenerationOptions>(),
-            It.IsAny<CancellationToken>()), Times.Once);
+        knowledgeServiceMock.Verify(s => s.SearchLibrarySemanticallyAsync(queryText, tenantId, 5, It.IsAny<CancellationToken>()), Times.Once);
     }
 
     [Fact]