Fix: Add confirmations support and fix notification logic

Webhook Improvements:
- Added Confirmations field to PaymentWebhookDto (default: 0)
- Updated webhook controller to pass confirmations to service layer
- Fixed notification logic to match order update conditions

Payment Confirmation Logic:
- Paid (2): Confirmed immediately regardless of confirmations
- Overpaid (3): Confirmed immediately regardless of confirmations
- Completed (7): Requires 3+ blockchain confirmations
- Notifications only sent when order is actually updated

This prevents premature notifications for unconfirmed 'Completed' status
while maintaining immediate processing for 'Paid' and 'Overpaid' statuses.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

LittleShop/Services/CryptoPaymentService.cs

@@ -139,7 +139,12 @@ public class CryptoPaymentService : ICryptoPaymentService
         payment.PaidAmount = amount;
         payment.TransactionHash = transactionHash;
 
-        if (status == PaymentStatus.Paid || status == PaymentStatus.Overpaid || (status == PaymentStatus.Completed && confirmations >= 3))
+        // Determine if payment is confirmed (ready to fulfill order)
+        var isPaymentConfirmed = status == PaymentStatus.Paid ||
+                                 status == PaymentStatus.Overpaid ||
+                                 (status == PaymentStatus.Completed && confirmations >= 3);
+
+        if (isPaymentConfirmed)
         {
             payment.PaidAt = DateTime.UtcNow;
 
@@ -156,8 +161,8 @@ public class CryptoPaymentService : ICryptoPaymentService
 
         await _context.SaveChangesAsync();
 
-        // Send notification for payment confirmation (including overpaid since payment was successful)
-        if (status == PaymentStatus.Paid || status == PaymentStatus.Overpaid || status == PaymentStatus.Completed)
+        // Send notification only when payment is confirmed and order is updated
+        if (isPaymentConfirmed)
         {
             await SendPaymentConfirmedNotification(payment.OrderId, amount);
         }