refactor: remove unused code and parameters from drag logic and document viewer

frontend/src/desktop/CardDragLogic.ts

@@ -33,7 +33,7 @@ export const handleDragStart = (store: LayoutStore, selection: string[], leading
     });
 };
 
-export const attachToDragGroup = (store: LayoutStore, selection: string[], leadingId: string, pointerId: number) => {
+export const attachToDragGroup = (store: LayoutStore, selection: string[], leadingId: string, _pointerId: number) => {
     const leadingCard = store.items.get(leadingId);
     if (!leadingCard || !leadingCard.physics.isDragging) return;
 

frontend/src/preview/DocumentViewerLayout.tsx

@@ -3,7 +3,6 @@ import type { JSX } from 'react';
 import DocumentInfoPanel from '../documents/DocumentInfoPanel';
 import PdfViewer from './PdfViewer';
 import MediaViewer from './MediaViewer';
-import { AUDIO_EXTENSIONS, VIDEO_EXTENSIONS } from '../constants/preview';
 
 import type { Document } from '../types/documents';
 
@@ -42,14 +41,6 @@ interface DocumentViewerLayoutProps {
   layoutMode?: LayoutMode;
 }
 
-const getFileExtension = (filename?: string | null) => {
-  if (!filename) {
-    return '';
-  }
-  const match = filename.toLowerCase().match(/\.([a-z0-9]+)$/);
-  return match ? match[1] : '';
-};
-
 const DocumentViewerLayout = ({
   document,
   documentLink,