fix(auth): inventoryApi - use apiFetch with /backend prefix and Authorization header

frontend/src/lib/inventoryApi.ts

@@ -1,14 +1,13 @@
+import { apiFetch } from './api';
 import type { EntityResponse, InventoryTreeNode, ListResponse, NodeContext, Relation } from '../types/inventory';
 
 async function handleResponse<T>(response: Response): Promise<T> {
-  if (!response.ok) {
-    throw new Error(`API error: ${response.status}`);
-  }
+  if (!response.ok) throw new Error(`API error: ${response.status}`);
   return response.json() as Promise<T>;
 }
 
-async function fetchJson<T>(url: string): Promise<T> {
-  const response = await fetch(url, { cache: 'no-store' });
+async function fetchJson<T>(path: string): Promise<T> {
+  const response = await apiFetch(path, { cache: 'no-store' });
   return handleResponse<T>(response);
 }