feat(user-center): add cash wallet balance separate from credits

Introduce AKSRT_Balance (user_meta aksrt_balance + balance_log) for
Zibll-like pay_balance wallet. User center assets panel shows wallet
and points; balance gateway/card-pass/refunds credit cash when enabled.

inc/classes/class-aksrt-payment-gateway.php

@@ -338,7 +338,7 @@ class AKSRT_Payment_Gateway {
 /**
  * 站内余额支付网关（内置实现）
  *
- * 使用积分/余额进行支付，无需第三方。
+ * 优先扣现金钱包（AKSRT_Balance / pay_balance）；未启用时回退到积分。
  */
 class AKSRT_Balance_Gateway implements AKSRT_Payment_Gateway_Interface {
 
@@ -351,7 +351,9 @@ class AKSRT_Balance_Gateway implements AKSRT_Payment_Gateway_Interface {
     }
 
     public function is_configured(): bool {
-        if (!class_exists('AKSRT_Credits')) {
+        $wallet_on = class_exists('AKSRT_Balance') && AKSRT_Balance::enabled();
+        $credits_on = class_exists('AKSRT_Credits');
+        if (!$wallet_on && !$credits_on) {
             return false;
         }
         if (class_exists('AKSRT_Settings_Payment_Runtime')) {
@@ -361,17 +363,43 @@ class AKSRT_Balance_Gateway implements AKSRT_Payment_Gateway_Interface {
     }
 
     public function create_payment(array $order): array {
+        $user_id = (int) ($order['user_id'] ?? 0);
+        $amount = round((float) ($order['amount'] ?? 0), 2);
+        $order_number = (string) ($order['order_number'] ?? '');
+
+        // Prefer cash wallet when pay_balance_s is on.
+        if (class_exists('AKSRT_Balance') && AKSRT_Balance::enabled()) {
+            if ($user_id <= 0) {
+                return ['success' => false, 'message' => __('请先登录', 'aksrt')];
+            }
+            $balance = AKSRT_Balance::balance($user_id);
+            if ($balance < $amount) {
+                return ['success' => false, 'message' => __('余额不足', 'aksrt')];
+            }
+            $result = AKSRT_Balance::deduct(
+                $user_id,
+                $amount,
+                'order_payment',
+                ['type' => 'order', 'id' => 0, 'order' => $order_number],
+                sprintf(__('订单 %s 支付', 'aksrt'), $order_number)
+            );
+            if (is_wp_error($result)) {
+                return ['success' => false, 'message' => $result->get_error_message() ?: __('扣款失败', 'aksrt')];
+            }
+            return [
+                'success'        => true,
+                'transaction_id' => 'BAL_' . ($order_number !== '' ? $order_number : (string) time()),
+                'message'        => __('余额支付成功', 'aksrt'),
+            ];
+        }
+
+        // Fallback: legacy points-as-balance (1 元 = 100 积分).
         if (!class_exists('AKSRT_Credits')) {
             return ['success' => false, 'message' => __('积分系统未启用', 'aksrt')];
         }
 
-        $user_id = (int) ($order['user_id'] ?? 0);
-        $amount = (float) ($order['amount'] ?? 0);
-        $credits_cost = (int) ceil($amount * 100); // 1 元 = 100 积分
-        $order_number = (string) ($order['order_number'] ?? '');
-
+        $credits_cost = (int) ceil($amount * 100);
         $balance = AKSRT_Credits::balance($user_id);
-
         if ($balance < $credits_cost) {
             return ['success' => false, 'message' => __('余额不足', 'aksrt')];
         }
@@ -416,10 +444,6 @@ class AKSRT_Balance_Gateway implements AKSRT_Payment_Gateway_Interface {
     }
 
     public function refund(string $order_number, float $amount): array {
-        if (!class_exists('AKSRT_Credits')) {
-            return ['success' => false, 'message' => __('积分系统未启用', 'aksrt')];
-        }
-
         $order_repo = AKSRT_Order_Repository::get_instance();
         $order = $order_repo->get($order_number);
 
@@ -428,8 +452,27 @@ class AKSRT_Balance_Gateway implements AKSRT_Payment_Gateway_Interface {
         }
 
         $user_id = (int) $order['user_id'];
-        $credits_refund = (int) ceil($amount * 100);
+        $amount = round((float) $amount, 2);
 
+        if (class_exists('AKSRT_Balance') && AKSRT_Balance::enabled()) {
+            $result = AKSRT_Balance::add(
+                $user_id,
+                $amount,
+                'order_refund',
+                ['type' => 'order', 'order' => $order_number],
+                sprintf(__('订单 %s 退款', 'aksrt'), $order_number)
+            );
+            if (is_wp_error($result)) {
+                return ['success' => false, 'message' => $result->get_error_message() ?: __('退款失败', 'aksrt')];
+            }
+            return ['success' => true, 'refund_id' => 'BAL_REF_' . $order_number, 'message' => __('退款成功', 'aksrt')];
+        }
+
+        if (!class_exists('AKSRT_Credits')) {
+            return ['success' => false, 'message' => __('积分系统未启用', 'aksrt')];
+        }
+
+        $credits_refund = (int) ceil($amount * 100);
         $result = AKSRT_Credits::add(
             $user_id,
             $credits_refund,