feat: Refactor utility and component exports, update dependencies, and add Knip for unused code detection.

frontend/src/preview/DocumentViewerPanel.tsx

@@ -23,7 +23,7 @@ import { resolveDocumentAssetUrl } from '../asset_manager';
 import PanelHeader from '../ui/PanelHeader';
 import BreadcrumbTrail from '../ui/BreadcrumbTrail';
 import DocumentViewerLayout from './DocumentViewerLayout';
-import useViewerLayoutMode from './useViewerLayoutMode';
+import { useViewerLayoutMode } from './useViewerLayoutMode';
 import { usePanelResizeBindings } from '../app/PanelManagerContext';
 import type { DocumentId, FolderId } from '../types/identifiers';
 import type { Document } from '../types/documents';
@@ -46,7 +46,7 @@ interface DocumentViewerPanelProps extends DocumentSummarySectionProps {
   sidebarMode?: SidebarMode;
 }
 
-export const createDocumentViewerHeaderActions = ({
+const createDocumentViewerHeaderActions = ({
   document,
   actionState,
   onZoom,

frontend/src/preview/MediaViewer.tsx

@@ -2,7 +2,7 @@ import React from 'react';
 import { DownloadIcon } from '../ui/icons';
 import { AUDIO_EXTENSIONS, VIDEO_EXTENSIONS } from '../constants/preview';
 
-export interface MediaViewerProps {
+interface MediaViewerProps {
     src: string;
     mimeType?: string;
     filename?: string;

frontend/src/preview/useViewerLayoutMode.ts

@@ -5,8 +5,6 @@ import {
   PORTRAIT_RATIO_STYLE_ID,
 } from '../constants/preview';
 
-export { DOCUMENT_VIEWER_PORTRAIT_HEIGHT_RATIO };
-
 const ensurePortraitRatioStyle = () => {
   const cssValue = String(DOCUMENT_VIEWER_PORTRAIT_HEIGHT_RATIO);
   const cssText = `:root { --document-viewer-portrait-height-ratio: ${cssValue}; }`;
@@ -78,5 +76,3 @@ export const useViewerLayoutMode = (
 
   return isStacked;
 };
-
-export default useViewerLayoutMode;