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/utils/file.ts

@@ -0,0 +1,53 @@
+/**
+ * 判断文件是否支持预览
+ */
+export function isPreviewable(mime: string | null | undefined): boolean {
+  if (!mime || mime === undefined) return false;
+  return (
+    mime.startsWith('image/') ||
+    mime.startsWith('video/') ||
+    mime === 'application/pdf' ||
+    mime.startsWith('text/')
+  );
+}
+
+/**
+ * 从 Directus 获取文件元信息
+ */
+export async function getFileMeta(id: string): Promise<FileMeta | null> {
+  const runtimeConfig = useRuntimeConfig();
+  const baseUrl = runtimeConfig.public.directus.url;
+  const access_token = runtimeConfig.public.directus.token;
+
+  try {
+    const response = await $fetch<{ data: DirectusFile }>(
+      `${baseUrl}/files/${id}`,
+      {
+        headers: {
+          Authorization: access_token ? `Bearer ${access_token}` : '',
+        },
+      }
+    );
+
+    const file = response.data;
+    if (!file) return null;
+
+    return {
+      id: file.id,
+      title: file.filename_disk ?? '',
+      filename_download: file.filename_download ?? '',
+      type: file.type ?? '',
+      filesize: Number(file.filesize),
+      width: file.width ?? undefined,
+      height: file.height ?? undefined,
+      uploaded_on: file.uploaded_on ?? undefined,
+      url: `${baseUrl}/assets/${file.id}`,
+      previewable: isPreviewable(file.type),
+    };
+  } catch (error) {
+    if (error instanceof Error) {
+      console.error('Error fetching file metadata:', error.message);
+    }
+    return null;
+  }
+}