perf(appointment): batch-fetch pending payments in expiry loop (fix N+1)

AppointmentExpiryService ran one findPendingByAppointment query per expiring
booking. Add PaymentRepository::findPendingByAppointments (one IN query keyed
by appointment id) and use it. Test covers expiry + payment cancellation for
several appointments at once.

src/Payment/Repository/PaymentRepository.php

@@ -62,6 +62,36 @@ class PaymentRepository extends ServiceEntityRepository
         ]);
     }
 
+    /**
+     * Batch variant of findPendingByAppointment: all pending payments for the
+     * given appointments in ONE query, keyed by appointment id. Avoids the N+1
+     * in AppointmentExpiryService when many bookings expire at once.
+     *
+     * @param Appointment[] $appointments
+     * @return array<int, Payment> appointment id => pending Payment
+     */
+    public function findPendingByAppointments(array $appointments): array
+    {
+        if ($appointments === []) {
+            return [];
+        }
+
+        $payments = $this->createQueryBuilder('p')
+            ->andWhere('p.appointment IN (:appointments)')
+            ->andWhere('p.status = :status')
+            ->setParameter('appointments', $appointments)
+            ->setParameter('status', Payment::STATUS_PENDING)
+            ->getQuery()
+            ->getResult();
+
+        $byAppointment = [];
+        foreach ($payments as $payment) {
+            $byAppointment[$payment->getAppointment()->getId()] = $payment;
+        }
+
+        return $byAppointment;
+    }
+
     public function save(Payment $entity, bool $flush = true): void
     {
         $this->getEntityManager()->persist($entity);