Revert inventory API to relative paths for Vite dev proxy

frontend/src/lib/inventoryApi.ts

@@ -4,22 +4,20 @@ async function handleResponse<T>(response: Response): Promise<T> {
   if (!response.ok) {
     throw new Error(`API error: ${response.status}`);
   }
-  const contentType = response.headers.get('content-type') || '';
-  if (!contentType.includes('application/json')) {
-    const text = await response.text();
-    throw new Error(`API returned non-JSON response: ${text.slice(0, 80)}`);
-  }
   return response.json() as Promise<T>;
 }
 
+async function fetchJson<T>(url: string): Promise<T> {
+  const response = await fetch(url, { cache: 'no-store' });
+  return handleResponse<T>(response);
+}
+
 export async function fetchInventoryTree(): Promise<InventoryTreeNode[]> {
-  const response = await fetch('http://127.0.0.1:8000/inventory/tree');
-  const data = await handleResponse<ListResponse<InventoryTreeNode>>(response);
+  const data = await fetchJson<ListResponse<InventoryTreeNode>>('/inventory/tree');
   return data.items;
 }
 
 export async function fetchNodeContext(id: string): Promise<NodeContext> {
-  const response = await fetch(`http://127.0.0.1:8000/inventory/nodes/${id}/context`);
-  const data = await handleResponse<EntityResponse<NodeContext>>(response);
+  const data = await fetchJson<EntityResponse<NodeContext>>(`/inventory/nodes/${id}/context`);
   return data.item;
 }