Add Payment module: contracts, payments/refunds tables, KBZ gateway, factory, orchestrator (T5.1-T5.7)

- T5.1 PaymentGatewayInterface, DTOs, PaymentMethod/PaymentStatus/RefundStatus enums
- T5.2 payments/refunds tables, models, factories
- T5.3-T5.5 KbzMiniAppGateway: initiate()/verify()/refund(), ported KBZ signing scheme,
  wired refund_amount through for partial refunds, mTLS options for refund
- T5.6 PaymentGatewayFactory resolving gateways by PaymentMethod
- T5.7 PaymentService orchestrator delegating to the resolved gateway

app-modules/payment/src/Services/PaymentService.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace Modules\Payment\Services;
+
+use Modules\Payment\Data\PaymentRequestData;
+use Modules\Payment\Data\PaymentResultData;
+use Modules\Payment\Data\RefundResultData;
+use Modules\Payment\Enums\PaymentMethod;
+use Modules\Payment\Factories\PaymentGatewayFactory;
+
+/**
+ * Thin orchestrator delegating to the gateway resolved by
+ * PaymentGatewayFactory — the single call site every Payment Action goes
+ * through, so no Action ever depends on a concrete gateway class.
+ */
+class PaymentService
+{
+    public function __construct(
+        private readonly PaymentGatewayFactory $gateways,
+    ) {}
+
+    public function initiate(PaymentRequestData $data): PaymentResultData
+    {
+        return $this->gateways->make($data->method)->initiate($data);
+    }
+
+    public function verify(PaymentMethod $method, string $gatewayTransactionId): PaymentResultData
+    {
+        return $this->gateways->make($method)->verify($gatewayTransactionId);
+    }
+
+    public function refund(PaymentMethod $method, string $gatewayTransactionId, string $amount, string $reason): RefundResultData
+    {
+        return $this->gateways->make($method)->refund($gatewayTransactionId, $amount, $reason);
+    }
+}