fix: Add missing useNavigate import in Orders Detail page

Fixed eslint error: "Cannot find name 'nav'"

Issue:
- Detail.tsx was using nav variable in useEffect
- useNavigate hook was not imported
- nav variable was not declared

Fix:
- Added useNavigate to imports from react-router-dom
- Declared nav variable: const nav = useNavigate()

Result:
✅ Zero eslint errors in Detail.tsx
✅ All Orders module files pass eslint

admin-spa/src/routes/Orders/Detail.tsx

@@ -1,5 +1,5 @@
 import React, { useEffect, useRef, useState } from 'react';
-import { useParams, useSearchParams, Link } from 'react-router-dom';
+import { useParams, useSearchParams, Link, useNavigate } from 'react-router-dom';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { api, OrdersApi } from '@/lib/api';
 import { formatRelativeOrDate } from '@/lib/dates';
@@ -44,6 +44,7 @@ const STATUS_OPTIONS = ['pending', 'processing', 'completed', 'on-hold', 'cancel
 export default function OrderShow() {
   const { id } = useParams<{ id: string }>();
   const qc = useQueryClient();
+  const nav = useNavigate();
   const siteTitle = (window as any).wnw?.siteTitle || 'WooNooW';
   const { setPageHeader, clearPageHeader } = usePageHeader();