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/computer-fundamentals/TransmissionDemo.vue

@@ -123,24 +123,30 @@
 </template>
 
 <script setup>
-import { ref, computed } from 'vue'
+import { ref, onUnmounted } from 'vue'
 
 const activeType = ref('serial')
-const dataBits = ref(['1', '0', '1', '1', '0', '0', '1', '0'])
+const dataBits = ref([1, 0, 1, 1, 0, 0, 1, 0])
 const receivedBits = ref(['-', '-', '-', '-', '-', '-', '-', '-'])
 const sendingBit = ref(null)
+const timer = ref(null)
+
+onUnmounted(() => {
+  if (timer.value) clearInterval(timer.value)
+})
 
 const startTransmission = () => {
+  if (timer.value) clearInterval(timer.value)
   if (activeType.value === 'serial') {
     receivedBits.value = ['-', '-', '-', '-', '-', '-', '-', '-']
     let i = 0
-    const interval = setInterval(() => {
+    timer.value = setInterval(() => {
       if (i < dataBits.value.length) {
         sendingBit.value = i
         receivedBits.value[i] = dataBits.value[i]
         i++
       } else {
-        clearInterval(interval)
+        if (timer.value) clearInterval(timer.value)
         sendingBit.value = null
       }
     }, 300)