feat: migrate payment provider to easy-pay, add order history and refund support

- Replace zpay with easy-pay payment provider (new lib/easy-pay/ module)
- Add order history page for users (pay/orders)
- Add GET /api/orders/my endpoint to list user's own orders
- Add GET /api/users/[id] endpoint for sub2api user lookup
- Add order status tracking module (lib/order/status.ts)
- Update config to support easy-pay credentials (merchant ID, key, gateway)
- Update PaymentForm and PaymentQRCode components for easy-pay flow
- Update pay page and admin page with new order management UI
- Update order service to support easy-pay, cancellation, and refund

src/app/pay/result/page.tsx

@@ -0,0 +1,110 @@
+'use client';
+
+import { useSearchParams } from 'next/navigation';
+import { useEffect, useState, Suspense } from 'react';
+
+function ResultContent() {
+  const searchParams = useSearchParams();
+  const outTradeNo = searchParams.get('out_trade_no');
+  const tradeStatus = searchParams.get('trade_status');
+
+  const [status, setStatus] = useState<string | null>(null);
+  const [loading, setLoading] = useState(true);
+
+  useEffect(() => {
+    if (!outTradeNo) {
+      setLoading(false);
+      return;
+    }
+
+    const checkOrder = async () => {
+      try {
+        const res = await fetch(`/api/orders/${outTradeNo}`);
+        if (res.ok) {
+          const data = await res.json();
+          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 () => {
+      clearInterval(timer);
+      clearTimeout(timeout);
+    };
+  }, [outTradeNo]);
+
+  if (loading) {
+    return (
+      <div className="flex min-h-screen items-center justify-center">
+        <div className="text-gray-500">查询支付结果中...</div>
+      </div>
+    );
+  }
+
+  const isSuccess = status === 'COMPLETED' || status === 'PAID' || status === 'RECHARGING';
+  const isPending = status === 'PENDING';
+
+  return (
+    <div className="flex min-h-screen items-center justify-center p-4">
+      <div className="w-full max-w-md rounded-xl bg-white p-8 text-center shadow-lg">
+        {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>
+            <p className="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...'}
+            </p>
+          </>
+        ) : 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="mt-2 text-gray-500">订单尚未完成支付</p>
+          </>
+        ) : (
+          <>
+            <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'}
+            </h1>
+            <p className="mt-2 text-gray-500">
+              {status === 'EXPIRED'
+                ? '订单已超时，请重新充值'
+                : status === 'CANCELLED'
+                  ? '订单已被取消'
+                  : '请联系管理员处理'}
+            </p>
+          </>
+        )}
+
+        <p className="mt-4 text-xs text-gray-400">
+          订单号: {outTradeNo || '未知'}
+        </p>
+      </div>
+    </div>
+  );
+}
+
+export default function PayResultPage() {
+  return (
+    <Suspense fallback={
+      <div className="flex min-h-screen items-center justify-center">
+        <div className="text-gray-500">加载中...</div>
+      </div>
+    }>
+      <ResultContent />
+    </Suspense>
+  );
+}