feat: 添加preview路由用于文件预览

- preview路由预览文件
- FilePreviewer组件
- 删除Document卡片的下载按钮，使用单独的页面用于文件下载
- preview布局

app/pages/preview/[id].vue

@@ -0,0 +1,13 @@
+<template>
+  <file-previewer :file-id="id" />
+</template>
+
+<script setup lang="ts">
+  definePageMeta({
+    layout: 'preview',
+  });
+
+  const route = useRoute();
+
+  const id = computed(() => route.params.id as string);
+</script>