fix: allow folderId in updateDocument and pass it through route handler

- Add folderId parameter to updateDocument service method
- Extract folderId from request body in PUT /documents/:id route
- Fixes move document to folder functionality

src/services/documentService.js

@@ -469,7 +469,7 @@ export class DocumentService {
     };
   }
 
-  async updateDocument(docId, { title, content, tags, type, priority, status }) {
+  async updateDocument(docId, { title, content, tags, type, priority, status, folderId }) {
     const found = this._findDocById(docId);
     if (!found) {
       throw new NotFoundError('Document');
@@ -484,6 +484,7 @@ export class DocumentService {
     if (priority !== undefined) meta.priority = priority;
     if (status !== undefined) meta.status = status;
     if (tags !== undefined) meta.tags = tags.filter(t => t);
+    if (folderId !== undefined) meta.folderId = folderId;
     meta.updatedAt = now;
 
     // Rewrite markdown file