feat: add comprehensive backend topics and fix build issues

## 新增内容

### 附录文档扩展
- 扩展前端项目架构文档 (frontend-project-architecture.md)
- 扩展后端项目架构文档 (backend-project-architecture.md)
- 扩展数据治理文档 (data-governance.md)
- 扩展数据可视化文档 (data-visualization.md)
- 扩展分布式系统文档 (distributed-systems.md)
- 扩展高可用文档 (high-availability.md)
- 扩展单体到微服务文档 (monolith-to-microservices.md)
- 扩展系统设计方法论文档 (system-design-methodology.md)
- 扩展 Docker 容器文档 (docker-containers.md)
- 扩展 Kubernetes 文档 (kubernetes.md)
- 扩展 Linux 基础文档 (linux-basics.md)
- 扩展神经网络文档 (neural-networks.md)

### 新增交互式组件
- 数据治理组件: DataQualityDemo, DataGovernanceFrameworkDemo, DataLineageDemo
- 数据可视化组件: ChartTypeSelectorDemo, DashboardLayoutDemo
- 分布式系统组件: CAPTheoremDemo, ConsistencyModelsDemo, DistributedChallengesDemo
- 高可用组件: AvailabilityCalculatorDemo, FailoverStrategyDemo
- 系统设计组件: SystemDesignStepsDemo, CapacityEstimationDemo
- Docker 容器组件: DockerArchitectureDemo, DockerLifecycleDemo
- Kubernetes 组件: K8sArchitectureDemo, K8sWorkloadsDemo
- Linux 基础组件: LinuxFileSystemDemo, LinuxCommandDemo, LinuxPermissionsDemo
- 神经网络组件: NeuronDemo, NetworkLayersDemo, NetworkArchitectureDemo
- 单体到微服务组件: ArchEvolutionDemo
- 项目架构组件: ProjectArchitectureComparisonDemo
- 附录导航组件: AppendixFlowMap

### 英文版重构
- 将 en-us 目录重命名为 en
- 更新相关配置和组件中的语言代码

## Bug 修复
- 修复 index.js 中重复的组件导入语句导致的 build 失败
- 恢复被注释的 InvertedIndexDemo 和 SearchRelevanceDemo 导入
- 修复 HomeFeatures.vue 中 en-us 与 config.mjs 中 en 不一致导致的语言切换问题

## 其他改进
- 添加构建脚本 (scripts/build.mjs)
- 更新依赖版本

docs/.vitepress/theme/components/appendix/data-visualization/DashboardLayoutDemo.vue

@@ -0,0 +1,134 @@
+<!--
+  DashboardLayoutDemo.vue
+  仪表盘布局演示：展示仪表盘的常见布局模式
+-->
+<template>
+  <div class="dashboard-demo">
+    <div class="header">
+      <div class="title">仪表盘布局模式</div>
+      <div class="subtitle">点击查看不同类型的仪表盘布局</div>
+    </div>
+
+    <div class="layout-tabs">
+      <div
+        v-for="layout in layouts"
+        :key="layout.key"
+        :class="['tab', { active: activeLayout === layout.key }]"
+        @click="activeLayout = layout.key"
+      >
+        {{ layout.name }}
+      </div>
+    </div>
+
+    <div v-if="current" class="layout-preview">
+      <div class="preview-title">{{ current.name }}</div>
+      <div class="preview-desc">{{ current.desc }}</div>
+      <div :class="['mock-dashboard', current.key]">
+        <div
+          v-for="(widget, i) in current.widgets"
+          :key="i"
+          :class="['widget', widget.type]"
+        >
+          <div class="widget-label">{{ widget.label }}</div>
+        </div>
+      </div>
+      <div class="use-case">适用场景：{{ current.useCase }}</div>
+    </div>
+  </div>
+</template>
+
+<script setup>
+import { ref, computed } from 'vue'
+
+const activeLayout = ref('overview')
+
+const layouts = [
+  {
+    key: 'overview',
+    name: '全局概览型',
+    desc: '顶部核心指标卡片 + 中间趋势图 + 底部明细表',
+    useCase: '管理层日报、运营大盘',
+    widgets: [
+      { type: 'kpi', label: 'DAU 12.5万' },
+      { type: 'kpi', label: '收入 ¥85万' },
+      { type: 'kpi', label: '转化率 3.2%' },
+      { type: 'kpi', label: '客单价 ¥268' },
+      { type: 'chart-wide', label: '趋势折线图' },
+      { type: 'table', label: '明细数据表' }
+    ]
+  },
+  {
+    key: 'comparison',
+    name: '对比分析型',
+    desc: '左右对比布局，适合 A/B 测试或同环比分析',
+    useCase: 'A/B 测试报告、竞品分析',
+    widgets: [
+      { type: 'half', label: '实验组指标' },
+      { type: 'half', label: '对照组指标' },
+      { type: 'chart-wide', label: '差异对比图' },
+      { type: 'table', label: '统计显著性检验' }
+    ]
+  },
+  {
+    key: 'drill',
+    name: '下钻分析型',
+    desc: '从汇总到明细逐层下钻，支持交互式探索',
+    useCase: '销售分析、用户行为分析',
+    widgets: [
+      { type: 'chart-wide', label: '全国销售地图（点击省份下钻）' },
+      { type: 'half', label: '省份排名柱状图' },
+      { type: 'half', label: '城市明细饼图' },
+      { type: 'table', label: '门店级明细表' }
+    ]
+  },
+  {
+    key: 'realtime',
+    name: '实时监控型',
+    desc: '大屏展示，数据自动刷新，适合投屏',
+    useCase: '双十一大屏、服务器监控',
+    widgets: [
+      { type: 'big-number', label: '实时 GMV ¥1.2亿' },
+      { type: 'half', label: '订单量实时曲线' },
+      { type: 'half', label: '地域热力图' },
+      { type: 'kpi', label: '支付成功率' },
+      { type: 'kpi', label: '平均响应时间' },
+      { type: 'kpi', label: '在线用户数' }
+    ]
+  }
+]
+
+const current = computed(() => layouts.find(l => l.key === activeLayout.value))
+</script>
+
+<style scoped>
+.dashboard-demo {
+  border: 1px solid var(--vp-c-divider); background: var(--vp-c-bg-soft);
+  border-radius: 12px; padding: 1.5rem; margin: 1.5rem 0;
+}
+.header { margin-bottom: 1rem; }
+.title { font-weight: 700; font-size: 1.1rem; }
+.subtitle { color: var(--vp-c-text-2); font-size: 0.9rem; }
+.layout-tabs { display: flex; gap: 0.5rem; margin-bottom: 1rem; flex-wrap: wrap; }
+.tab {
+  padding: 0.4rem 0.75rem; border-radius: 6px; cursor: pointer;
+  font-size: 0.85rem; background: var(--vp-c-bg); border: 1px solid var(--vp-c-divider);
+  transition: all 0.2s;
+}
+.tab:hover { border-color: var(--vp-c-brand); }
+.tab.active { border-color: var(--vp-c-brand); background: rgba(var(--vp-c-brand-rgb), 0.05); font-weight: 600; }
+.layout-preview { background: var(--vp-c-bg); border-radius: 8px; padding: 1rem; border: 1px solid var(--vp-c-divider); }
+.preview-title { font-weight: 700; font-size: 0.95rem; }
+.preview-desc { color: var(--vp-c-text-2); font-size: 0.82rem; margin-bottom: 0.75rem; }
+.mock-dashboard { display: grid; gap: 0.4rem; margin-bottom: 0.75rem; grid-template-columns: repeat(4, 1fr); }
+.widget {
+  padding: 0.5rem; border-radius: 6px; text-align: center;
+  font-size: 0.75rem; font-weight: 600; border: 1px dashed var(--vp-c-divider);
+}
+.widget.kpi { background: rgba(var(--vp-c-brand-rgb), 0.06); grid-column: span 1; }
+.widget.chart-wide { background: rgba(34,197,94,0.06); grid-column: span 4; min-height: 50px; }
+.widget.table { background: rgba(245,158,11,0.06); grid-column: span 4; }
+.widget.half { background: rgba(99,102,241,0.06); grid-column: span 2; min-height: 40px; }
+.widget.big-number { background: rgba(239,68,68,0.06); grid-column: span 4; min-height: 40px; font-size: 0.9rem; }
+.widget-label { color: var(--vp-c-text-2); }
+.use-case { font-size: 0.82rem; color: var(--vp-c-text-3); }
+</style>