refactor: extract various constants

frontend/src/preview/DocumentViewerLayout.tsx

@@ -3,6 +3,7 @@ import type { JSX } from 'react';
 import DocumentInfoPanel from '../documents/DocumentInfoPanel';
 import { DownloadIcon } from '../ui/icons';
 import PdfViewer from './PdfViewer';
+import { AUDIO_EXTENSIONS, VIDEO_EXTENSIONS } from '../constants/preview';
 
 interface DocumentLike {
   id?: string;
@@ -48,29 +49,6 @@ interface DocumentViewerLayoutProps {
   layoutMode?: LayoutMode;
 }
 
-const AUDIO_EXTENSIONS = new Set([
-  'aac',
-  'aiff',
-  'flac',
-  'm4a',
-  'mp3',
-  'ogg',
-  'oga',
-  'opus',
-  'wav',
-  'weba',
-]);
-
-const VIDEO_EXTENSIONS = new Set([
-  'avi',
-  'mkv',
-  'mov',
-  'mp4',
-  'm4v',
-  'webm',
-  'wmv',
-]);
-
 const getFileExtension = (filename?: string | null) => {
   if (!filename) {
     return '';