more work on attachments

* fix frontend env usage

apps/server/src/helpers/file.helper.ts

@@ -0,0 +1,7 @@
+import * as mime from 'mime-types';
+import * as path from 'node:path';
+
+export function getMimeType(filePath: string): string {
+  const ext = path.extname(filePath);
+  return mime.contentType(ext) || 'application/octet-stream';
+}

apps/server/src/helpers/index.ts

@@ -1 +1,3 @@
 export * from './utils';
+export * from './nanoid.utils';
+export * from './file.helper';