feat(pay): 统一收银台四种模式（站内二维码/当前页跳转/表单提交/JSAPI）

- PaymentOrchestrator 统一返回 mode + code_url/payment_url/form_html/jsapi_params
- 支付宝：当面付二维码 / 电脑网站支付 / H5；微信：Native / H5 / JSAPI（WechatOpenid 静默授权）
- 易支付：PC mapi 二维码，移动端自动提交表单
- 删除旧键 alipay_payment_type / wechat_payment_type / epay_device 与 redirect/qr_content 字段
- 新增 pay-cashier.js，移除 window.open，订单状态接口改为 /pay/order/{n}
- 拆分 credits.js（affiliate / withdraw-history）至 1000 行以内

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

src/Settings/PaymentRuntime.php

@@ -410,7 +410,7 @@ class PaymentRuntime {
                 'apiurl' => esc_url_raw((string) ($settings['epay_apiurl'] ?? '')),
                 'pid'    => sanitize_text_field((string) ($settings['epay_pid'] ?? '')),
                 'key'    => sanitize_text_field((string) ($settings['epay_key'] ?? '')),
-                'device' => sanitize_key((string) ($settings['epay_device'] ?? 'auto')),
+                'qrcode' => !array_key_exists('epay_qrcode', $settings) || !empty($settings['epay_qrcode']),
             ],
         ];
     }