feat: 添加完整的前端管理系统 (VbenAdmin)

- 添加基于 VbenAdmin + Vue3 + Element Plus 的前端管理系统
- 包含完整的 UI 组件库和工具链
- 支持多应用架构 (web-ele, backend-mock, playground)
- 包含完整的开发规范和配置
- 修复 admin 目录的子模块问题，确保正确提交

admin/docs/src/demos/vben-drawer/auto-height/drawer.vue

@@ -0,0 +1,45 @@
+<script lang="ts" setup>
+import { ref } from 'vue';
+
+import { useVbenDrawer, VbenButton } from '@vben/common-ui';
+
+const list = ref<number[]>([]);
+
+const [Drawer, drawerApi] = useVbenDrawer({
+  onCancel() {
+    drawerApi.close();
+  },
+  onConfirm() {
+    console.log('onConfirm');
+  },
+  onOpenChange(isOpen) {
+    if (isOpen) {
+      handleUpdate(10);
+    }
+  },
+});
+
+function handleUpdate(len: number) {
+  drawerApi.setState({ loading: true });
+  setTimeout(() => {
+    list.value = Array.from({ length: len }, (_v, k) => k + 1);
+    drawerApi.setState({ loading: false });
+  }, 2000);
+}
+</script>
+<template>
+  <Drawer title="自动计算高度">
+    <div
+      v-for="item in list"
+      :key="item"
+      class="even:bg-heavy bg-muted flex-center h-[220px] w-full"
+    >
+      {{ item }}
+    </div>
+    <template #prepend-footer>
+      <VbenButton type="link" @click="handleUpdate(6)">
+        点击更新数据
+      </VbenButton>
+    </template>
+  </Drawer>
+</template>