feat(intelligence): implement Global AI Q&A screen and paywall blocker

- Implemented standard empty and active chat conversation states for the `/intelligence` page
- Created interactive `AiResponseRenderer` with AOT-compliant sentence splitting and payment gateway simulation
- Added scoped `LibraryStateService` to synchronize book ownership and updates across the application
- Obfuscated paywalled content in DOM to prevent inspection bypass
- Fixed local port connection mismatch by updating API configurations to use port 5104

src/NexusReader.Web/Program.cs

@@ -57,6 +57,7 @@ builder.Services.AddScoped<IReaderNavigationService, ReaderNavigationService>();
 builder.Services.AddScoped<IKnowledgeGraphService, KnowledgeGraphService>();
 builder.Services.AddScoped<IReaderInteractionService, ReaderInteractionService>();
 builder.Services.AddScoped<IReaderStateService, ReaderStateService>();
+builder.Services.AddScoped<ILibraryStateService, LibraryStateService>();
 builder.Services.AddScoped<KnowledgeCoordinator>();
 builder.Services.AddScoped<ISyncService, SyncService>();
 
@@ -454,6 +455,48 @@ app.MapGet("/api/library/books", async (ClaimsPrincipal user, IMediator mediator
     return Results.BadRequest(errorMsg);
 }).RequireAuthorization();
 
+app.MapPost("/api/library/purchase", async (
+    ClaimsPrincipal user,
+    [FromBody] PurchaseBookRequest request,
+    IDbContextFactory<AppDbContext> dbContextFactory) =>
+{
+    var userId = user.FindFirstValue(ClaimTypes.NameIdentifier);
+    if (string.IsNullOrEmpty(userId)) return Results.Unauthorized();
+
+    using var dbContext = await dbContextFactory.CreateDbContextAsync();
+    
+    // Find or create author
+    var authorName = "Nexus Architect";
+    var author = await dbContext.Authors.FirstOrDefaultAsync(a => a.Name == authorName);
+    if (author == null)
+    {
+        author = new Author { Name = authorName };
+        dbContext.Authors.Add(author);
+        await dbContext.SaveChangesAsync();
+    }
+
+    // Check if the book already exists for the user
+    var bookExists = await dbContext.Ebooks.AnyAsync(e => e.UserId == userId && e.Title == request.Title);
+    if (!bookExists)
+    {
+        var newBook = new Ebook
+        {
+            Title = request.Title,
+            AuthorId = author.Id,
+            UserId = userId,
+            FilePath = "wwwroot/assets/book.epub",
+            AddedDate = DateTime.UtcNow,
+            Progress = 0,
+            Description = "Zaawansowany kurs budowania skalowalnych SaaS z Native AOT, CQRS, MediatR, FluentResults i izolowanym systemem stylów Blazor CSS.",
+            IsReadyForReading = true
+        };
+        dbContext.Ebooks.Add(newBook);
+        await dbContext.SaveChangesAsync();
+    }
+
+    return Results.Ok();
+}).RequireAuthorization();
+
 app.MapGet("/api/book/{bookId:guid}/concepts-map", async (
     Guid bookId,
     ClaimsPrincipal user,
@@ -729,3 +772,4 @@ public record KnowledgeRequest(string Text, Guid? EbookId = null);
 public record GroundednessRequest(string Answer, string Context);
 public record SemanticSearchRequest(string QueryText, int Limit = 5);
 public record AskQuestionRequest(string Question, Guid? EbookId = null, int Limit = 5);
+public record PurchaseBookRequest(string Title);