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/storage/contact.json

@@ -0,0 +1,22 @@
+[
+  {
+    "id": "CT1774007263178",
+    "createdAt": "2026-03-20T11:47:43.178Z",
+    "name": "李女士",
+    "phone": "13711112222",
+    "subject": "询问秋季团期",
+    "message": "请问9月底有哪些团期可以选择？",
+    "ip": "::1",
+    "source": "contact-form"
+  },
+  {
+    "id": "CT1774023293117",
+    "createdAt": "2026-03-20T16:14:53.117Z",
+    "name": "测试用户",
+    "phone": "13800138000",
+    "subject": "行程咨询",
+    "message": "请问七月份有空档吗，想带家人来",
+    "ip": "::1",
+    "source": "contact-form"
+  }
+]

server/storage/customize.json

@@ -0,0 +1,107 @@
+[
+  {
+    "id": "CZ1774007128348",
+    "createdAt": "2026-03-20T11:45:28.348Z",
+    "name": "测试用户",
+    "phone": "13800138000",
+    "wechat": "",
+    "adults": 2,
+    "children": 1,
+    "childAges": [
+      5
+    ],
+    "date": "2026-07-01",
+    "duration": "5d4n",
+    "activities": [
+      "骑马",
+      "露营"
+    ],
+    "budget": "1-2万",
+    "remarks": "这是测试提交",
+    "ip": "::1",
+    "source": "customize-form"
+  },
+  {
+    "id": "CZ1774007220100",
+    "createdAt": "2026-03-20T11:47:00.100Z",
+    "name": "王小明",
+    "phone": "13912345678",
+    "wechat": "wxid_test",
+    "adults": 2,
+    "children": 2,
+    "childAges": [
+      6,
+      9
+    ],
+    "date": "2026-08-15",
+    "duration": "6d5n",
+    "activities": [
+      "骑马",
+      "露营",
+      "捕鱼"
+    ],
+    "budget": "2-3万",
+    "remarks": "希望住蒙古包",
+    "ip": "::1",
+    "source": "customize-form"
+  },
+  {
+    "id": "CZ1774023293092",
+    "createdAt": "2026-03-20T16:14:53.092Z",
+    "name": "测试用户",
+    "phone": "13800138000",
+    "wechat": "",
+    "adults": 2,
+    "children": 1,
+    "childAges": [
+      5
+    ],
+    "date": "2026-07-15",
+    "duration": "6d5n",
+    "activities": [],
+    "budget": "8000-12000",
+    "remarks": "",
+    "ip": "::1",
+    "source": "customize-form"
+  },
+  {
+    "id": "CZ1774057315225",
+    "createdAt": "2026-03-21T01:41:55.225Z",
+    "name": "测试用户",
+    "phone": "13800138000",
+    "wechat": "",
+    "adults": 2,
+    "children": 1,
+    "childAges": [],
+    "date": "",
+    "duration": "6天5晚",
+    "activities": [
+      "骑马",
+      "旅拍"
+    ],
+    "budget": "品质优先",
+    "remarks": "",
+    "ip": "::1",
+    "source": "customize-form"
+  },
+  {
+    "id": "CZ1774335344590",
+    "createdAt": "2026-03-24T06:55:44.590Z",
+    "name": "发电公司",
+    "phone": "17600545225",
+    "wechat": "",
+    "adults": 2,
+    "children": 0,
+    "childAges": [],
+    "date": "2026-03-26",
+    "duration": "5天4晚",
+    "activities": [
+      "亲子活动",
+      "旅拍"
+    ],
+    "budget": "5000-8000元",
+    "remarks": "第三方公司代发",
+    "ip": "::1",
+    "source": "customize-form"
+  }
+]