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/Payment/Gateways/YansongdaPayFactory.php

@@ -187,21 +187,6 @@ class YansongdaPayFactory {
 		return '';
 	}
 
-	/**
-	 * HTML body from alipay Response (form auto-submit) when no Location header.
-	 *
-	 * @param mixed $result
-	 */
-	public static function extract_html_body($result): string {
-		if ($result instanceof \Psr\Http\Message\ResponseInterface) {
-			if ($result->getHeaderLine('Location') !== '') {
-				return '';
-			}
-			return (string) $result->getBody();
-		}
-		return '';
-	}
-
 	/**
 	 * Emit SDK success()/fail() ResponseInterface (or string) and exit.
 	 *