feat: add Vue2 exercises for dynamic styles, lifecycle methods, component communication, and course management dashboard

- Implement dynamic styles and event handling in Vue2 with a card component.
- Create lifecycle methods exercise to simulate async data loading and instance destruction.
- Develop a component communication exercise with props, events, and slots.
- Build a comprehensive course management dashboard with filtering, statistics, and component interactions.

07-vue2/07-lifecycle-and-async/README.md

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+# 练习 7：生命周期和异步更新
+
+## 目标
+
+学会在合适的生命周期里加载数据，并理解页面更新的时机。
+
+## 你要练什么
+
+- `created`
+- `mounted`
+- `updated`
+- `beforeDestroy`
+- `destroyed`
+- 模拟异步请求
+
+## 任务
+
+请基于页面结构完成以下操作：
+
+- 进入页面时显示 loading
+- 在 `mounted` 里模拟异步获取课程数据
+- 数据返回后渲染课程列表
+- 在 `updated` 里输出更新日志
+- 点击按钮时销毁当前实例，并观察销毁日志
+
+## 文件
+
+- [starter.html](/Users/lijiaqing/home/wwwroot/front-end-example/07-vue2/07-lifecycle-and-async/starter.html)
+- [starter.js](/Users/lijiaqing/home/wwwroot/front-end-example/07-vue2/07-lifecycle-and-async/starter.js)
+- [answer.html](/Users/lijiaqing/home/wwwroot/front-end-example/07-vue2/07-lifecycle-and-async/answer.html)
+- [answer.js](/Users/lijiaqing/home/wwwroot/front-end-example/07-vue2/07-lifecycle-and-async/answer.js)