feat: Add an Ollama-based PDF OCR script and refactor frontend folder tree management with a new FoldersManager and useSyncExternalStore.

frontend/src/documents/features/folders/useFolderTree.ts

@@ -1,7 +1,7 @@
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import { getFolderTree, listFolderContents } from '../../../lib/api/apiClient';
 import type { Dispatch, MutableRefObject, SetStateAction } from 'react';
-import { createRootNode, DEFAULT_FOLDER_NAME } from '../../../app/workspaceUtils';
+import { createRootNode, DEFAULT_FOLDER_NAME, flattenFolderTree } from '../../../app/workspaceUtils';
 import {
   getEntryId,
   isDocumentEntry,
@@ -76,10 +76,13 @@ const useFolderTree = ({
           const next = new Map(prev);
           const rootChildren: FolderNodeId[] = [];
 
-          data.forEach((item) => {
+          const flatData = flattenFolderTree(data);
+
+          flatData.forEach((item) => {
             const id = item.id as FolderNodeId;
             const parentId = (item.parent_id || 'root') as FolderNodeId;
-            const children = (item.children || []).map((c) => c as FolderNodeId);
+            // item.children is now FolderTreeNode[], so map to IDs
+            const children = (item.children || []).map((c) => c.id as FolderNodeId);
 
             next.set(id, {
               id,