refactor(ui): 重构侧边栏导航结构并更新组件配置

- 移除嵌套子菜单结构，简化为平铺式菜单项
- 添加首页路由导航项，优化导航体验
- 更新 .gitignore 文件，忽略 package-lock.json
- 注释掉 AboutView 中的动态按钮渲染逻辑
- 在组件声明文件中添加 ElSubItem 组件类型定义
- 调整侧边栏样式，固定宽度为 200px 并优化高度计算

flask-ui/components.d.ts

@@ -35,6 +35,7 @@ declare module 'vue' {
     ElSelect: typeof import('element-plus/es')['ElSelect']
     ElSplitter: typeof import('element-plus/es')['ElSplitter']
     ElSplitterPanel: typeof import('element-plus/es')['ElSplitterPanel']
+    ElSubItem: typeof import('element-plus/es')['ElSubItem']
     ElSubMenu: typeof import('element-plus/es')['ElSubMenu']
     RouterLink: typeof import('vue-router')['RouterLink']
     RouterView: typeof import('vue-router')['RouterView']
@@ -69,6 +70,7 @@ declare global {
   const ElSelect: typeof import('element-plus/es')['ElSelect']
   const ElSplitter: typeof import('element-plus/es')['ElSplitter']
   const ElSplitterPanel: typeof import('element-plus/es')['ElSplitterPanel']
+  const ElSubItem: typeof import('element-plus/es')['ElSubItem']
   const ElSubMenu: typeof import('element-plus/es')['ElSubMenu']
   const RouterLink: typeof import('vue-router')['RouterLink']
   const RouterView: typeof import('vue-router')['RouterView']