refactor: consolidate project structure by migrating authentication, identity, and shared UI components while removing legacy Web Client files.

src/NexusReader.Domain/Entities/NexusUser.cs

@@ -0,0 +1,34 @@
+using Microsoft.AspNetCore.Identity;
+
+namespace NexusReader.Domain.Entities;
+
+/// <summary>
+/// Extended Identity user for the Nexus AI E-Reader SaaS platform.
+/// </summary>
+public class NexusUser : IdentityUser
+{
+    /// <summary>
+    /// Total number of AI tokens allowed for the current billing period.
+    /// </summary>
+    public int AITokenLimit { get; set; }
+
+    /// <summary>
+    /// Number of AI tokens consumed in the current billing period.
+    /// </summary>
+    public int AITokensUsed { get; set; }
+
+    /// <summary>
+    /// Unique identifier for the tenant (SaaS multi-tenancy support).
+    /// </summary>
+    public Guid TenantId { get; set; }
+
+    /// <summary>
+    /// Current subscription plan (e.g., "Free", "Pro", "Enterprise").
+    /// </summary>
+    public string CurrentPlan { get; set; } = "Free";
+
+    /// <summary>
+    /// Collection of e-books owned by the user.
+    /// </summary>
+    public ICollection<Ebook> Ebooks { get; set; } = new List<Ebook>();
+}