feat(ui/graph): Knowledge Graph Refinement and Sidebar Hierarchy (#25)

This PR addresses several UI/UX and architectural refinements for the Knowledge Graph and Intelligence Sidebar.

### Key Changes:
- **Knowledge Graph (#21, #22)**:
  - Implemented \"pill-shaped\" nodes with dynamic label truncation and SVG tooltips.
  - Added bound-constrained simulation to keep nodes within the viewport.
  - Integrated `ResizeObserver` for dynamic layout handling.
  - Implemented Zoom-to-Fit functionality.
  - Enforced unique concept IDs in AI prompts and hardened JS logic to prevent multi-selection bugs.
- **Intelligence Sidebar (#23)**:
  - Improved visual depth with a radial gradient background for the graph.
  - Increased sidebar divider contrast for better layering.
  - Transformed graph controls into a floating glassmorphism panel.
  - Relocated the \"Logout\" action to the toolbar bottom and rebranded it as \"Exit\".

Fixes #21
Fixes #22
Fixes #23

Reviewed-on: #25
Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Co-committed-by: Marek Jasiński <jasins.marek@gmail.com>

src/NexusReader.Infrastructure/Handlers/UpdateReadingProgressCommandHandler.cs

@@ -38,9 +38,18 @@ public class UpdateReadingProgressCommandHandler : IRequestHandler<UpdateReading
         await context.SaveChangesAsync(cancellationToken);
 
         // Broadcast to other devices
-        await _hubContext.Clients
-            .Group($"User_{request.UserId}")
-            .SendAsync("ProgressUpdated", request.PageId, now, cancellationToken);
+        var group = _hubContext.Clients.Group($"User_{request.UserId}");
+        
+        if (!string.IsNullOrEmpty(request.ExcludedConnectionId))
+        {
+            await _hubContext.Clients
+                .GroupExcept($"User_{request.UserId}", request.ExcludedConnectionId)
+                .SendAsync("ProgressUpdated", request.PageId, now, cancellationToken);
+        }
+        else
+        {
+            await group.SendAsync("ProgressUpdated", request.PageId, now, cancellationToken);
+        }
 
         return Result.Ok();
     }