refactor: introduce dedicated identifier types for improved clarity and type safety

frontend/src/app/useDocumentPreview.ts

@@ -5,8 +5,8 @@ import type {
   SetStateAction,
 } from 'react';
 import { fetchDocument } from '../lib/apiClient';
+import type { DocumentId } from '../types/identifiers';
 
-type DocumentId = string | number;
 type FolderId = DocumentId | 'root';
 
 type DocumentLike = {
@@ -102,7 +102,7 @@ const useDocumentPreview = ({
     async (documentId: DocumentId, { force = false }: { force?: boolean } = {}): Promise<DocumentLink | null> => {
       if (!documentId) return null;
 
-    const existing = documentLinks.get(documentId);
+      const existing = documentLinks.get(documentId);
       const now = Date.now();
       const expiresAt = existing?.expiresAt ?? null;
       if (!force && existing && (!expiresAt || expiresAt > now)) {