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>

components/contact/ContactChannel.vue

@@ -0,0 +1,43 @@
+<template>
+  <CommonContentCard :class="{ 'channel-primary': channel.primary }">
+    <div class="channel">
+      <span v-if="channel.primary" class="channel-badge">推荐</span>
+      <h3 class="channel-label">{{ channel.label }}</h3>
+      <p class="channel-value">{{ channel.value }}</p>
+      <p v-if="channel.description" class="channel-desc">{{ channel.description }}</p>
+      <CommonQRCodeBlock
+        v-if="channel.qrImage"
+        :image="channel.qrImage"
+        :label="channel.label"
+        size="normal"
+      />
+    </div>
+  </CommonContentCard>
+</template>
+
+<script setup>
+defineProps({ channel: { type: Object, required: true } })
+</script>
+
+<style lang="less" scoped>
+.channel { text-align: center; }
+.channel-label { font-size: @font-size-md; color: @color-primary; margin-bottom: @space-sm; }
+.channel-value { font-size: @font-size-base; color: @color-text-primary; font-weight: @font-weight-medium; margin-bottom: @space-xs; }
+.channel-desc { font-size: @font-size-sm; color: @color-text-muted; margin-bottom: @space-md; }
+
+.channel-primary {
+  border: 2px solid @color-primary;
+  position: relative;
+}
+
+.channel-badge {
+  display: inline-block;
+  padding: @space-xs @space-md;
+  font-size: @font-size-xs;
+  font-weight: @font-weight-medium;
+  color: #fff;
+  background: @color-primary;
+  border-radius: @border-radius-full;
+  margin-bottom: @space-md;
+}
+</style>

components/contact/ContactMap.vue

@@ -0,0 +1,14 @@
+<template>
+  <div class="contact-map">
+    <p class="map-address">{{ address }}</p>
+  </div>
+</template>
+
+<script setup>
+defineProps({ address: { type: String, required: true } })
+</script>
+
+<style lang="less" scoped>
+.contact-map { padding: @space-lg; background: @color-bg-gray; border-radius: @border-radius-md; text-align: center; }
+.map-address { color: @color-text-secondary; }
+</style>