feat(payment): tighten gateways and implement Epay

Keep only balance, Alipay, WeChat, PayPal, Stripe, Epay, and card-pass
channels; remove placeholder aggregators. Add dual-channel Epay gateway
with MD5 notify/return, register cashier methods, and gate card-pass
redeem behind the payment channel switch.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/AKSRT/Shop/ProductService.php

@@ -95,24 +95,12 @@ class ProductService {
             ];
         }
 
-        $manual = true;
-        if (class_exists('\AKSRT\Settings\Settings')) {
-            $gw = \AKSRT\Settings\Settings::get_payment_gateway_settings();
-            $manual = !empty($gw['manual_review']) || ($gw['mode'] ?? '') === 'manual_review';
-        }
-        if ($manual) {
-            $methods['manual_review'] = [
-                'value'       => 'manual_review',
-                'label'       => __('人工确认', 'aksrt'),
-                'description' => __('保留待支付订单，后续由管理员确认。', 'aksrt'),
-            ];
-        }
-
+        // Fallback only when no configured gateways (and no points).
         if (empty($methods)) {
             $methods['manual_review'] = [
                 'value'       => 'manual_review',
                 'label'       => __('人工确认', 'aksrt'),
-                'description' => __('保留待支付订单，后续由管理员确认。', 'aksrt'),
+                'description' => __('暂无可用支付网关，保留待支付订单由管理员确认。', 'aksrt'),
             ];
         }
 
@@ -131,6 +119,10 @@ class ProductService {
                 return __('跳转 PayPal 完成支付。', 'aksrt');
             case 'stripe':
                 return __('跳转 Stripe Checkout 完成支付。', 'aksrt');
+            case 'epay_alipay':
+                return __('经易支付跳转支付宝完成支付。', 'aksrt');
+            case 'epay_wxpay':
+                return __('经易支付跳转微信完成支付。', 'aksrt');
             default:
                 return '';
         }