Decouple UserType, add Role entity and management

Removed all UserType logic and references, replacing them with a new Role model and management system. Introduced RoleManager service, repository, and API endpoint for role CRUD operations. Updated user flows and JWT claims to use RoleCode. Removed admin-only user CRUD endpoints. Updated DI, documentation, and error handling for consistency. Appsettings and DTOs now reflect the new role-based approach.

Models/User.cs

@@ -30,13 +30,8 @@ namespace AuthHex.Models
         public bool IsMfaEnabled { get; set; }
         public UserMfa? UserMfa { get; set; }
 
-        // Roles are not an authentication concern: the ERP owns a person's role and permissions (users.RoleId in ERPCore).
-        // AuthHex only says who the person is. (The old Users.RoleId column is left in the table, nullable and unmapped,
-        // until it is dropped - see Docs/migrations/2026-10-remove-roles.sql.)
-        public Guid UserTypeId { get; set; }
-        public UserType? UserType { get; set; }
-
-
+        //User Role and Type
+        public string? RoleCode { get; set; }
         public ICollection<UserSession>? Sessions { get; set; }
         public ICollection<UserProvider>? Providers { get; set; }
     }