feat: implement cross-device reading progress synchronization using SignalR and remove legacy quiz generation services.

src/NexusReader.Infrastructure/DependencyInjection.cs

@@ -65,7 +65,6 @@ public static class DependencyInjection
         }));
 
         services.AddScoped<IKnowledgeService, KnowledgeService>();
-        services.AddTransient<IAiGenerateQuizService, FakeAiGenerateQuizService>();
         services.AddTransient<IEpubService, EpubService>();
 
         services.AddAuthorizationCore(options =>
@@ -75,6 +74,11 @@ public static class DependencyInjection
 
         services.AddScoped<IAuthorizationHandler, ProUserHandler>();
 
+        services.AddMediatR(config => 
+        {
+            config.RegisterServicesFromAssembly(typeof(DependencyInjection).Assembly);
+        });
+
         return services;
     }
 }

src/NexusReader.Infrastructure/Handlers/UpdateReadingProgressCommandHandler.cs

@@ -0,0 +1,46 @@
+using FluentResults;
+using MediatR;
+using Microsoft.AspNetCore.SignalR;
+using Microsoft.EntityFrameworkCore;
+using NexusReader.Application.Commands.Sync;
+using NexusReader.Domain.Entities;
+using NexusReader.Infrastructure.Persistence;
+using NexusReader.Infrastructure.RealTime;
+
+namespace NexusReader.Infrastructure.Handlers;
+
+public class UpdateReadingProgressCommandHandler : IRequestHandler<UpdateReadingProgressCommand, Result>
+{
+    private readonly AppDbContext _context;
+    private readonly IHubContext<SyncHub> _hubContext;
+
+    public UpdateReadingProgressCommandHandler(
+        AppDbContext context, 
+        IHubContext<SyncHub> hubContext)
+    {
+        _context = context;
+        _hubContext = hubContext;
+    }
+
+    public async Task<Result> Handle(UpdateReadingProgressCommand request, CancellationToken cancellationToken)
+    {
+        var user = await _context.Users.FirstOrDefaultAsync(u => u.Id == request.UserId, cancellationToken);
+        if (user == null)
+        {
+            return Result.Fail("User not found.");
+        }
+
+        var now = DateTime.UtcNow;
+        user.LastReadPageId = request.PageId;
+        user.LastReadAt = now;
+
+        await _context.SaveChangesAsync(cancellationToken);
+
+        // Broadcast to other devices
+        await _hubContext.Clients
+            .Group($"User_{request.UserId}")
+            .SendAsync("ProgressUpdated", request.PageId, now, cancellationToken);
+
+        return Result.Ok();
+    }
+}

src/NexusReader.Infrastructure/NexusReader.Infrastructure.csproj

@@ -1,9 +1,13 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
-  <ItemGroup>
-    <ProjectReference Include="..\NexusReader.Application\NexusReader.Application.csproj" />
-  </ItemGroup>
-
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <ItemGroup>
+    <ProjectReference Include="..\NexusReader.Application\NexusReader.Application.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <FrameworkReference Include="Microsoft.AspNetCore.App" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="GeminiDotnet.Extensions.AI" Version="0.23.0" />
     <PackageReference Include="Microsoft.AspNetCore.Authorization" Version="10.0.7" />

src/NexusReader.Infrastructure/Persistence/AppDbContext.cs

@@ -16,6 +16,12 @@ public class AppDbContext : IdentityDbContext<NexusUser>
 
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
+        modelBuilder.Entity<NexusUser>(entity =>
+        {
+            entity.Property(u => u.LastReadPageId).HasMaxLength(255);
+            entity.Property(u => u.LastReadAt).IsRequired(false);
+        });
+
         base.OnModelCreating(modelBuilder);
 
         modelBuilder.Entity<SemanticKnowledgeCache>(entity =>

src/NexusReader.Infrastructure/RealTime/SyncHub.cs

@@ -0,0 +1,46 @@
+using MediatR;
+using Microsoft.AspNetCore.SignalR;
+using Microsoft.AspNetCore.Authorization;
+using NexusReader.Application.Commands.Sync;
+
+namespace NexusReader.Infrastructure.RealTime;
+
+[Authorize]
+public class SyncHub : Hub
+{
+    private readonly IMediator _mediator;
+
+    public SyncHub(IMediator mediator)
+    {
+        _mediator = mediator;
+    }
+
+    public async Task UpdateProgress(string pageId)
+    {
+        var userId = Context.UserIdentifier;
+        if (!string.IsNullOrEmpty(userId))
+        {
+            await _mediator.Send(new UpdateReadingProgressCommand(pageId, userId));
+        }
+    }
+
+    public override async Task OnConnectedAsync()
+    {
+        var userId = Context.UserIdentifier;
+        if (!string.IsNullOrEmpty(userId))
+        {
+            await Groups.AddToGroupAsync(Context.ConnectionId, $"User_{userId}");
+        }
+        await base.OnConnectedAsync();
+    }
+
+    public override async Task OnDisconnectedAsync(Exception? exception)
+    {
+        var userId = Context.UserIdentifier;
+        if (!string.IsNullOrEmpty(userId))
+        {
+            await Groups.RemoveFromGroupAsync(Context.ConnectionId, $"User_{userId}");
+        }
+        await base.OnDisconnectedAsync(exception);
+    }
+}

src/NexusReader.Infrastructure/Services/FakeAiGenerateQuizService.cs

@@ -1,23 +0,0 @@
-using FluentResults;
-using NexusReader.Application.Abstractions.Services;
-using NexusReader.Application.Queries.Quiz;
-
-namespace NexusReader.Infrastructure.Services;
-
-public sealed class FakeAiGenerateQuizService : IAiGenerateQuizService
-{
-    public async Task<Result<QuizDto>> GenerateQuizAsync(string contextBlockId, CancellationToken cancellationToken = default)
-    {
-        // 2000ms delay to highlight Skeleton loader visually
-        await Task.Delay(2000, cancellationToken);
-
-        var fakeQuiz = new List<QuizQuestionDto>
-        {
-            new("Co było głównym centrum włoskiego Renesansu?", new List<string> { "Wenecja", "Rzym", "Florencja", "Mediolan" }, 2),
-            new("Kto stanowił wpływowy ród mecenasów sztuki?", new List<string> { "Habsburgowie", "Medyceusze", "Borgiowie", "Sforzowie" }, 1),
-            new("Jaką koncepcją filozoficzną charakteryzował się renesans?", new List<string> { "Teocentryzmem", "Nihilizmem", "Humanizmem", "Egzystencjalizmem" }, 2)
-        };
-
-        return Result.Ok(new QuizDto(fakeQuiz));
-    }
-}