fix grouping functionality

frontend/src/nodeHierarchy.js

@@ -0,0 +1,28 @@
+export function sortNodesForParentOrder(nodes) {
+  const list = Array.isArray(nodes) ? nodes.filter(Boolean) : [];
+  const entries = list.map((node) => ({ id: String(node.id), node }));
+  const byId = new Map(entries.map((entry) => [entry.id, entry]));
+  const visiting = new Set();
+  const visited = new Set();
+  const ordered = [];
+
+  function visit(entry) {
+    if (!entry) return;
+    const { id, node } = entry;
+    if (visited.has(id) || visiting.has(id)) return;
+
+    visiting.add(id);
+
+    const parentId = node?.parentId ? String(node.parentId) : null;
+    if (parentId) {
+      visit(byId.get(parentId));
+    }
+
+    visiting.delete(id);
+    visited.add(id);
+    ordered.push(node);
+  }
+
+  entries.forEach((entry) => visit(entry));
+  return ordered;
+}