feat: 全站多语言支持 (i18n)，lang=en 显示英文，其余默认中文

新增 src/lib/locale.ts 作为统一多语言入口，覆盖前台支付链路、
管理后台、API/服务层错误文案，共 35 个文件。URL 参数 lang 全链路透传，
包括 Stripe return_url、页面跳转、layout html lang 属性等。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/pay/result/page.tsx

@@ -2,22 +2,43 @@
 
 import { useSearchParams } from 'next/navigation';
 import { useEffect, useState, Suspense } from 'react';
+import { applyLocaleToSearchParams, pickLocaleText, resolveLocale } from '@/lib/locale';
 
 function ResultContent() {
   const searchParams = useSearchParams();
-  // Support both ZPAY (out_trade_no) and Stripe (order_id) callback params
   const outTradeNo = searchParams.get('out_trade_no') || searchParams.get('order_id');
-  const tradeStatus = searchParams.get('trade_status') || searchParams.get('status');
   const isPopup = searchParams.get('popup') === '1';
   const theme = searchParams.get('theme') === 'dark' ? 'dark' : 'light';
+  const locale = resolveLocale(searchParams.get('lang'));
   const isDark = theme === 'dark';
 
+  const text = {
+    checking: pickLocaleText(locale, '查询支付结果中...', 'Checking payment result...'),
+    success: pickLocaleText(locale, '充值成功', 'Top-up successful'),
+    processing: pickLocaleText(locale, '充值处理中', 'Top-up processing'),
+    successMessage: pickLocaleText(locale, '余额已成功到账！', 'Balance has been credited successfully!'),
+    processingMessage: pickLocaleText(locale, '支付成功，余额正在充值中...', 'Payment succeeded, balance is being credited...'),
+    returning: pickLocaleText(locale, '正在返回...', 'Returning...'),
+    returnNow: pickLocaleText(locale, '立即返回', 'Return now'),
+    pending: pickLocaleText(locale, '等待支付', 'Awaiting payment'),
+    pendingMessage: pickLocaleText(locale, '订单尚未完成支付', 'The order has not been paid yet'),
+    expired: pickLocaleText(locale, '订单已超时', 'Order expired'),
+    cancelled: pickLocaleText(locale, '订单已取消', 'Order cancelled'),
+    abnormal: pickLocaleText(locale, '支付异常', 'Payment error'),
+    expiredMessage: pickLocaleText(locale, '订单已超时，请重新充值', 'This order has expired. Please create a new one.'),
+    cancelledMessage: pickLocaleText(locale, '订单已被取消', 'This order has been cancelled.'),
+    abnormalMessage: pickLocaleText(locale, '请联系管理员处理', 'Please contact the administrator.'),
+    back: pickLocaleText(locale, '返回', 'Back'),
+    orderId: pickLocaleText(locale, '订单号', 'Order ID'),
+    unknown: pickLocaleText(locale, '未知', 'Unknown'),
+    loading: pickLocaleText(locale, '加载中...', 'Loading...'),
+  };
+
   const [status, setStatus] = useState<string | null>(null);
   const [loading, setLoading] = useState(true);
   const [isInPopup, setIsInPopup] = useState(false);
   const [countdown, setCountdown] = useState(5);
 
-  // Detect if opened as a popup window (from stripe-popup or via popup=1 param)
   useEffect(() => {
     if (isPopup || window.opener) {
       setIsInPopup(true);
@@ -38,14 +59,12 @@ function ResultContent() {
           setStatus(data.status);
         }
       } catch {
-        // ignore
       } finally {
         setLoading(false);
       }
     };
 
     checkOrder();
-    // Poll a few times in case status hasn't updated yet
     const timer = setInterval(checkOrder, 3000);
     const timeout = setTimeout(() => clearInterval(timer), 30000);
     return () => {
@@ -59,14 +78,20 @@ function ResultContent() {
   const goBack = () => {
     if (isInPopup) {
       window.close();
-    } else if (window.history.length > 1) {
-      window.history.back();
-    } else {
-      window.close();
+      return;
     }
+
+    if (window.history.length > 1) {
+      window.history.back();
+      return;
+    }
+
+    const params = new URLSearchParams();
+    params.set('theme', theme);
+    applyLocaleToSearchParams(params, locale);
+    window.location.replace(`/pay?${params.toString()}`);
   };
 
-  // Countdown auto-return on success
   useEffect(() => {
     if (!isSuccess) return;
     setCountdown(5);
@@ -81,18 +106,18 @@ function ResultContent() {
       });
     }, 1000);
     return () => clearInterval(timer);
-    // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [isSuccess, isInPopup]);
 
   if (loading) {
     return (
       <div className={`flex min-h-screen items-center justify-center ${isDark ? 'bg-slate-950' : 'bg-slate-50'}`}>
-        <div className={isDark ? 'text-slate-400' : 'text-gray-500'}>查询支付结果中...</div>
+        <div className={isDark ? 'text-slate-400' : 'text-gray-500'}>{text.checking}</div>
       </div>
     );
   }
 
   const isPending = status === 'PENDING';
+  const countdownText = countdown > 0 ? pickLocaleText(locale, `${countdown} 秒后自动返回`, `${countdown} seconds before returning`) : text.returning;
 
   return (
     <div className={`flex min-h-screen items-center justify-center p-4 ${isDark ? 'bg-slate-950' : 'bg-slate-50'}`}>
@@ -105,78 +130,79 @@ function ResultContent() {
         {isSuccess ? (
           <>
             <div className="text-6xl text-green-500">✓</div>
-            <h1 className="mt-4 text-xl font-bold text-green-600">
-              {status === 'COMPLETED' ? '充值成功' : '充值处理中'}
-            </h1>
+            <h1 className="mt-4 text-xl font-bold text-green-600">{status === 'COMPLETED' ? text.success : text.processing}</h1>
             <p className={isDark ? 'mt-2 text-slate-400' : 'mt-2 text-gray-500'}>
-              {status === 'COMPLETED' ? '余额已成功到账！' : '支付成功，余额正在充值中...'}
+              {status === 'COMPLETED' ? text.successMessage : text.processingMessage}
             </p>
             <div className="mt-4 space-y-2">
-              <p className={isDark ? 'text-sm text-slate-500' : 'text-sm text-gray-400'}>
-                {countdown > 0 ? `${countdown} 秒后自动返回` : '正在返回...'}
-              </p>
+              <p className={isDark ? 'text-sm text-slate-500' : 'text-sm text-gray-400'}>{countdownText}</p>
               <button
                 type="button"
                 onClick={goBack}
                 className="text-sm text-blue-600 underline hover:text-blue-700"
               >
-                立即返回
+                {text.returnNow}
               </button>
             </div>
           </>
         ) : isPending ? (
           <>
             <div className="text-6xl text-yellow-500">⏳</div>
-            <h1 className="mt-4 text-xl font-bold text-yellow-600">等待支付</h1>
-            <p className={isDark ? 'mt-2 text-slate-400' : 'mt-2 text-gray-500'}>订单尚未完成支付</p>
+            <h1 className="mt-4 text-xl font-bold text-yellow-600">{text.pending}</h1>
+            <p className={isDark ? 'mt-2 text-slate-400' : 'mt-2 text-gray-500'}>{text.pendingMessage}</p>
             <button
               type="button"
               onClick={goBack}
               className="mt-4 text-sm text-blue-600 underline hover:text-blue-700"
             >
-              返回
+              {text.back}
             </button>
           </>
         ) : (
           <>
             <div className="text-6xl text-red-500">✗</div>
             <h1 className="mt-4 text-xl font-bold text-red-600">
-              {status === 'EXPIRED' ? '订单已超时' : status === 'CANCELLED' ? '订单已取消' : '支付异常'}
+              {status === 'EXPIRED' ? text.expired : status === 'CANCELLED' ? text.cancelled : text.abnormal}
             </h1>
             <p className={isDark ? 'mt-2 text-slate-400' : 'mt-2 text-gray-500'}>
               {status === 'EXPIRED'
-                ? '订单已超时，请重新充值'
+                ? text.expiredMessage
                 : status === 'CANCELLED'
-                  ? '订单已被取消'
-                  : '请联系管理员处理'}
+                  ? text.cancelledMessage
+                  : text.abnormalMessage}
             </p>
             <button
               type="button"
               onClick={goBack}
               className="mt-4 text-sm text-blue-600 underline hover:text-blue-700"
             >
-              返回
+              {text.back}
             </button>
           </>
         )}
 
         <p className={isDark ? 'mt-4 text-xs text-slate-500' : 'mt-4 text-xs text-gray-400'}>
-          订单号: {outTradeNo || '未知'}
+          {text.orderId}: {outTradeNo || text.unknown}
         </p>
       </div>
     </div>
   );
 }
 
+function ResultPageFallback() {
+  const searchParams = useSearchParams();
+  const locale = resolveLocale(searchParams.get('lang'));
+
+  return (
+    <div className="flex min-h-screen items-center justify-center bg-slate-50">
+      <div className="text-gray-500">{pickLocaleText(locale, '加载中...', 'Loading...')}</div>
+    </div>
+  );
+}
+
 export default function PayResultPage() {
   return (
-    <Suspense
-      fallback={
-        <div className="flex min-h-screen items-center justify-center bg-slate-50">
-          <div className="text-gray-500">加载中...</div>
-        </div>
-      }
-    >
+    <Suspense fallback={<ResultPageFallback />}>
       <ResultContent />
     </Suspense>
   );