refactor: 前端构建按需化与 Mock 懒加载

移除全量 Element Plus 与全局 VChart 注册，改为按需引入样式与组件内局部图表；Mock 适配器改为按 VITE_ENABLE_MOCK 环境变量懒加载，生产默认不拦截请求；ECharts 精简为看板所需图表，各视图与 stores 同步适配。

frontend/src/views/system/HardwareView.vue

@@ -1,6 +1,8 @@
 <script setup lang="ts">
 import { computed, nextTick, onMounted, onUnmounted, ref } from 'vue'
+import VChart from 'vue-echarts'
 import PageCard from '@/components/PageCard.vue'
+import '@/plugins/echarts-hardware'
 import { getSystemInfo } from '@/api/modules/system'
 import type { GpuInfo, SystemInfo } from '@/types'