feat: 添加download路由用于展示文档信息

- 添加/download/documentID路由用于文档下载
- server端添加文档元数据获取与下载API
- 将app中的types移至shared，与server共享

server/api/download/[id].ts

@@ -0,0 +1,22 @@
+import { getFileMeta } from '../../utils/file';
+
+export default defineEventHandler(async (event) => {
+  const id = getRouterParam(event, 'id');
+  if (!id) {
+    throw createError({ statusCode: 400, message: '缺少文件ID' });
+  }
+  const file = await getFileMeta(id);
+  if (!file) {
+    throw createError({ statusCode: 404, message: '文件不存在' });
+  }
+
+  const res = await $fetch<ArrayBuffer>(file.url, {
+    responseType: 'arrayBuffer',
+  });
+  return new Response(res, {
+    headers: {
+      'Content-Disposition': `attachment; filename="${encodeURIComponent(file.filename_download)}"`,
+      'Content-Type': file.type,
+    },
+  });
+});