feat(payment): add refund and reversal functionality to payment gateways

- Implemented `refund` and `reverse` methods in `PaymentGatewayInterface`.
- Added `PaymentRefundResult` class to handle refund operation results.
- Enhanced `MockGateway` and `SepGateway` to support refund and reversal operations.
- Updated `PaymentManager` to include `refundPayment` and `reversePayment` methods for handling refunds and reversals in transactions.
- Modified `ClinicSubscriptionRepository` and `SubscriptionService` to manage subscriptions during refunds.
- Added admin API endpoints for processing refunds and reversals.
- Updated security headers to allow form actions to the sandbox environment.
- Documented the new refund and reversal features in the API documentation.

src/Subscription/Service/SubscriptionService.php

@@ -115,6 +115,15 @@ class SubscriptionService
         return $subscription;
     }
 
+    /** حذف اشتراکِ ساخته‌شده از یک پرداخت (هنگام استرداد/برگشت وجه). */
+    public function deleteByPayment(\App\Payment\Entity\Payment $payment): void
+    {
+        $subscription = $this->subscriptionRepo->findByPayment($payment);
+        if ($subscription !== null) {
+            $this->subscriptionRepo->remove($subscription);
+        }
+    }
+
     public function calculateExpiresAt(?int $currentExpiresAt, int $durationMonths): int
     {
         $base = max($currentExpiresAt ?? 0, time());