Add customer communication system

LittleShop/Models/Order.cs

@@ -9,9 +9,12 @@ public class Order
     [Key]
     public Guid Id { get; set; }
     
-    [Required]
+    // Customer Information (nullable for transition period)
+    public Guid? CustomerId { get; set; }
+    
+    // Legacy identity reference (still used for anonymous orders)
     [StringLength(100)]
-    public string IdentityReference { get; set; } = string.Empty;
+    public string? IdentityReference { get; set; }
     
     public OrderStatus Status { get; set; } = OrderStatus.PendingPayment;
     
@@ -57,6 +60,7 @@ public class Order
     public DateTime? ShippedAt { get; set; }
     
     // Navigation properties
+    public virtual Customer? Customer { get; set; }
     public virtual ICollection<OrderItem> Items { get; set; } = new List<OrderItem>();
     public virtual ICollection<CryptoPayment> Payments { get; set; } = new List<CryptoPayment>();
 }