Add React inventory UI with tree and node context panel

frontend/src/lib/inventoryApi.ts

@@ -0,0 +1,20 @@
+import type { EntityResponse, InventoryTreeNode, ListResponse, NodeContext } from '../types/inventory';
+
+async function handleResponse<T>(response: Response): Promise<T> {
+  if (!response.ok) {
+    throw new Error(`API error: ${response.status}`);
+  }
+  return response.json() as Promise<T>;
+}
+
+export async function fetchInventoryTree(): Promise<InventoryTreeNode[]> {
+  const response = await fetch('/api/inventory/tree');
+  const data = await handleResponse<ListResponse<InventoryTreeNode>>(response);
+  return data.items;
+}
+
+export async function fetchNodeContext(id: string): Promise<NodeContext> {
+  const response = await fetch(`/api/inventory/nodes/${id}/context`);
+  const data = await handleResponse<EntityResponse<NodeContext>>(response);
+  return data.item;
+}