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/api/users/[id]/route.ts

@@ -0,0 +1,34 @@
+import { NextResponse } from 'next/server';
+import { getUser } from '@/lib/sub2api/client';
+
+export async function GET(
+  _request: Request,
+  { params }: { params: Promise<{ id: string }> },
+) {
+  const { id } = await params;
+  const userId = Number(id);
+
+  if (!Number.isInteger(userId) || userId <= 0) {
+    return NextResponse.json({ error: 'Invalid user id' }, { status: 400 });
+  }
+
+  try {
+    const user = await getUser(userId);
+    const displayName = user.username || user.email || `User #${user.id}`;
+
+    return NextResponse.json({
+      id: user.id,
+      username: user.username,
+      email: user.email,
+      displayName,
+      balance: user.balance,
+      status: user.status,
+    });
+  } catch (error) {
+    if (error instanceof Error && error.message === 'USER_NOT_FOUND') {
+      return NextResponse.json({ error: 'User not found' }, { status: 404 });
+    }
+    console.error('Get user info error:', error);
+    return NextResponse.json({ error: 'Get user info failed' }, { status: 500 });
+  }
+}