feat: 后台管理系统完整重构 + 前后台数据联通

- 后台全面引入 Naive UI 组件库，统一 UI 规范
- 前台 usePublicApi 切换到 API 调用（GET /api/content/[key]）
- 前后台数据源统一（site_content 表）
- 产品线统一管理（tour/camp/course 三套编辑器）
- 产品数据归一化（itinerary/faq/pricing 格式统一）
- 表单提交 API 改写入 submissions 表
- 新增 submissions 标记已读 API
- site-content PUT 支持 upsert
- 修复前台 bug（stories 路由冲突、占位符警告、selector breadcrumb）
- 消除 PageHero 类型警告（useSEO reactive 修复）
- 25 个前台页面全部 HTTP 200，展示效果不变

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/routes/sitemap.xml.js

@@ -0,0 +1,70 @@
+export default defineEventHandler((event) => {
+  const pages = [
+    {
+      url: '/', priority: '1.0', changefreq: 'weekly',
+      images: [{ loc: '/images/team/hero-grassland.jpg', title: '呼伦贝尔草原风光 - 呼籁旅行' }],
+    },
+    {
+      url: '/faq', priority: '0.95', changefreq: 'weekly',
+      images: [],
+    },
+    {
+      url: '/products', priority: '0.9', changefreq: 'weekly',
+      images: [{ loc: '/images/mascot/xiaomengma.png', title: '小蒙马夏令营IP形象' }],
+    },
+    {
+      url: '/about', priority: '0.85', changefreq: 'monthly',
+      images: [
+        { loc: '/images/team/hero-family.jpg', title: '呼伦贝尔家庭游合影' },
+        { loc: '/images/team/guide-group.jpg', title: '呼籁旅行领队团队合影' },
+        { loc: '/images/mascot/mascot-front.png', title: '呼籁旅行吉祥物' },
+      ],
+    },
+    {
+      url: '/reviews', priority: '0.8', changefreq: 'weekly',
+      images: [],
+    },
+    {
+      url: '/contact', priority: '0.8', changefreq: 'monthly',
+      images: [{ loc: '/images/contact/qrcode-wechat.jpg', title: '呼籁旅行微信客服二维码' }],
+    },
+    {
+      url: '/guides', priority: '0.8', changefreq: 'monthly',
+      images: [],
+    },
+    {
+      url: '/summer-camp', priority: '0.85', changefreq: 'monthly',
+      images: [
+        { loc: '/images/summer-camp/river-banner.jpg', title: '小蒙马夏令营河畔活动' },
+        { loc: '/images/summer-camp/grassland-group.jpg', title: '草原亲子夏令营合影' },
+        { loc: '/images/summer-camp/birch-group.jpg', title: '白桦林研学活动' },
+        { loc: '/images/summer-camp/camp-graduation.jpg', title: '夏令营结营仪式' },
+      ],
+    },
+  ]
+
+  const today = new Date().toISOString().split('T')[0]
+  const base = 'https://1814.love'
+
+  const xml = `<?xml version="1.0" encoding="UTF-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
+        xmlns:image="http://www.google.com/schemas/sitemap-image/1.1">
+${pages
+  .map(
+    (p) => `  <url>
+    <loc>${base}${p.url}</loc>
+    <lastmod>${today}</lastmod>
+    <changefreq>${p.changefreq}</changefreq>
+    <priority>${p.priority}</priority>${p.images.map(img => `
+    <image:image>
+      <image:loc>${base}${img.loc}</image:loc>
+      <image:title>${img.title}</image:title>
+    </image:image>`).join('')}
+  </url>`
+  )
+  .join('\n')}
+</urlset>`
+
+  setResponseHeader(event, 'content-type', 'application/xml')
+  return xml
+})