feat(payment): finish Zibll key contract and wire checkout gateways

Drop dual-read payment runtime fallbacks, align PHP schema to Vue keys,
read gateway credentials only from aksrt_settings with enable toggles,
expose configured adapters at checkout, fix credits pay signatures, and
apply order expiry settings. Wire orphan order/card-pass/withdrawal
schema pages; delete unused Payment* wrappers.

inc/classes/gateways/class-aksrt-paypal-gateway.php

@@ -20,6 +20,10 @@ class AKSRT_PayPal_Gateway implements AKSRT_Payment_Gateway_Interface {
     }
 
     public function is_configured(): bool {
+        if (class_exists('AKSRT_Settings_Payment_Runtime')
+            && !AKSRT_Settings_Payment_Runtime::is_gateway_enabled('paypal')) {
+            return false;
+        }
         $config = $this->get_config();
         return !empty($config['client_id']) && !empty($config['client_secret']);
     }
@@ -128,21 +132,16 @@ class AKSRT_PayPal_Gateway implements AKSRT_Payment_Gateway_Interface {
     }
 
     private function get_config(): array {
-        // 优先从统一设置读取（schema 保存的 key）
-        if (class_exists('AKSRT_Settings')) {
-            $all = AKSRT_Settings::get_all();
-            if (!empty($all['paypal_client_id'])) {
-                return [
-                    'client_id'     => $all['paypal_client_id'] ?? '',
-                    'client_secret' => $all['paypal_client_secret'] ?? '',
-                    'currency'      => $all['paypal_currency'] ?? 'USD',
-                    'mode'          => !empty($all['paypal_sandbox']) ? 'sandbox' : 'live',
-                ];
-            }
+        if (!class_exists('AKSRT_Settings')) {
+            return [];
         }
-        // 回退到独立 option
-        $settings = get_option('aksrt_payment_paypal', []);
-        return is_array($settings) ? $settings : [];
+        $all = AKSRT_Settings::get_all();
+        return [
+            'client_id'     => (string) ($all['paypal_client_id'] ?? ''),
+            'client_secret' => (string) ($all['paypal_client_secret'] ?? ''),
+            'currency'      => (string) ($all['paypal_currency'] ?? 'USD'),
+            'mode'          => !empty($all['paypal_sandbox']) ? 'sandbox' : 'live',
+        ];
     }
 
     /**