refactor: extract various constants

frontend/src/documents/DocumentThumbnailImage.tsx

@@ -5,6 +5,7 @@ import {
   resolveDocumentAssetUrl,
   resolveAssetUrl,
 } from '../asset_manager';
+import { DEFAULT_THUMBNAIL_SIZE } from '../constants/documents';
 import type {
   DocumentLike as AssetManagerDocumentLike,
   AssetLike as AssetManagerAssetLike,
@@ -12,8 +13,6 @@ import type {
   GetAsset as AssetManagerGetAsset,
 } from '../asset_manager';
 
-const DEFAULT_THUMBNAIL_SIZE = 48;
-
 // Detect when an element becomes visible within a scroll container so we can delay loading.
 const useLazyVisibility = (
   rootRef: MutableRefObject<Element | null> | null,