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/ReaderNavigationService.cs

@@ -1,4 +1,3 @@
-using System.Linq;
 using Microsoft.AspNetCore.Components;
 
 namespace NexusReader.UI.Shared.Services;
@@ -12,6 +11,7 @@ public class ReaderNavigationService : IReaderNavigationService
         _navigationManager = navigationManager;
     }
 
+    public Guid CurrentEbookId { get; private set; } = Guid.Empty;
     public int CurrentChapterIndex { get; private set; } = 0;
     public int TotalChapters { get; private set; } = 1;
     public string ChapterTitle { get; private set; } = "Loading...";
@@ -21,7 +21,7 @@ public class ReaderNavigationService : IReaderNavigationService
     public async Task GoToChapter(int index)
     {
         if (index < 0 || index >= TotalChapters) return;
-        
+
         CurrentChapterIndex = index;
         await NotifyNavigationChangedAsync();
     }
@@ -48,7 +48,7 @@ public class ReaderNavigationService : IReaderNavigationService
         if (CurrentChapterIndex != currentIndex) { CurrentChapterIndex = currentIndex; changed = true; }
         if (TotalChapters != totalChapters) { TotalChapters = totalChapters; changed = true; }
         if (ChapterTitle != title) { ChapterTitle = title; changed = true; }
-        
+
         if (changed)
         {
             await NotifyNavigationChangedAsync();
@@ -57,6 +57,8 @@ public class ReaderNavigationService : IReaderNavigationService
 
     public void NavigateToBook(Guid bookId)
     {
+        CurrentEbookId = bookId;
+        CurrentChapterIndex = 0;
         _navigationManager.NavigateTo($"/reader/{bookId}");
     }