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/lib/admin-auth.ts

@@ -0,0 +1,19 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { getEnv } from '@/lib/config';
+import crypto from 'crypto';
+
+export function verifyAdminToken(request: NextRequest): boolean {
+  const token = request.nextUrl.searchParams.get('token');
+  if (!token) return false;
+
+  const env = getEnv();
+  const expected = Buffer.from(env.ADMIN_TOKEN);
+  const received = Buffer.from(token);
+
+  if (expected.length !== received.length) return false;
+  return crypto.timingSafeEqual(expected, received);
+}
+
+export function unauthorizedResponse() {
+  return NextResponse.json({ error: '未授权' }, { status: 401 });
+}