feat: Ingestion Pipeline Stabilization and WASM Service Proxies (#42)

This PR stabilizes the Nexus Ingestion Engine by implementing functional service proxies for the Blazor WASM client and refining the backend infrastructure for real-time progress tracking and database compatibility.

### Key Changes
- **Infrastructure Stabilization**:
  - Implemented production-grade `EbookRepository` with PostgreSQL `EF.Functions.ILike` support.
  - Enforced `IsReadyForReading = false` state for newly added ebooks (resolves #35).
  - Updated `SignalRSyncBroadcaster` to support targeted user messaging and ingestion-specific progress updates (resolves #37).
- **WASM Client Functional Proxies**:
  - Replaced "Throwing" dummy services with `WasmEbookRepository`, `WasmSyncBroadcaster`, `WasmBookStorageService`, and `WasmEmbeddingGenerator`.
  - These services proxy requests to the backend via a new set of Minimal API endpoints in `NexusReader.Web`.
- **Domain Refinement**:
  - Added `IsReadyForReading` flag to the `Ebook` entity to manage background AI processing states.

### Related Issues
- Fixes #35
- Fixes #36
- Fixes #37

---------

Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Reviewed-on: #42
Co-authored-by: Antigravity <antigravity@google.com>
Co-committed-by: Antigravity <antigravity@google.com>

src/NexusReader.UI.Shared/Services/SyncService.cs

@@ -1,7 +1,7 @@
 using FluentResults;
 using Microsoft.AspNetCore.SignalR.Client;
+using Microsoft.Extensions.Logging;
 using NexusReader.Application.Abstractions.Services;
-using System.Net.Http;
 
 namespace NexusReader.UI.Shared.Services;
 
@@ -10,6 +10,7 @@ public class SyncService : ISyncService, IAsyncDisposable
     private readonly HttpClient _httpClient;
     private readonly INativeStorageService _storageService;
     private readonly IPlatformService _platformService;
+    private readonly ILogger<SyncService> _logger;
     private HubConnection? _hubConnection;
     private bool _isInitialized;
     private CancellationTokenSource? _debounceCts;
@@ -19,11 +20,13 @@ public class SyncService : ISyncService, IAsyncDisposable
     public SyncService(
         HttpClient httpClient,
         INativeStorageService storageService,
-        IPlatformService platformService)
+        IPlatformService platformService,
+        ILogger<SyncService> logger)
     {
         _httpClient = httpClient;
         _storageService = storageService;
         _platformService = platformService;
+        _logger = logger;
     }
 
     public async Task<Result> InitializeAsync()
@@ -78,9 +81,9 @@ public class SyncService : ISyncService, IAsyncDisposable
             try
             {
                 await Task.Delay(2000, token);
-                
+
                 if (!_isInitialized) await InitializeAsync();
-                
+
                 if (_hubConnection?.State == HubConnectionState.Connected)
                 {
                     await _hubConnection.SendAsync("UpdateProgress", pageId, ebookId, progress, chapterTitle, token);
@@ -90,7 +93,7 @@ public class SyncService : ISyncService, IAsyncDisposable
             catch (TaskCanceledException) { /* Ignored, user kept scrolling */ }
             catch (Exception ex)
             {
-                Console.WriteLine($"[SyncService] Error sending progress: {ex.Message}");
+                _logger.LogError(ex, "[SyncService] Error sending reading progress for page {PageId}.", pageId);
             }
         }, token);