refactor: migrate demo applications to playground (#4116)

* chore: detail adjustment

* refactor: Migrate demo applications to playground

* perf: logic optimization

* chore: update docs

* chore: update docs

playground/src/views/demos/access/admin-visible.vue

@@ -0,0 +1,11 @@
+<script lang="ts" setup>
+import { Fallback } from '@vben/common-ui';
+</script>
+
+<template>
+  <Fallback
+    description="当前页面仅 Admin 账号可见"
+    status="coming-soon"
+    title="页面访问测试"
+  />
+</template>