feat(frontend): add API client, layout, and routing

- Create Axios-based API client with sources, jobs, and dashboard endpoints
- Add responsive Layout component with navigation sidebar
- Set up React Router with Dashboard, Backups, and Settings routes
- Configure TanStack Query provider with default options
- Use lucide-react for navigation icons

frontend/node_modules/dom-helpers/esm/remove.js

@@ -0,0 +1,13 @@
+/**
+ * Removes a given node from the DOM.
+ * 
+ * @param node the node to remove
+ */
+export default function remove(node) {
+  if (node && node.parentNode) {
+    node.parentNode.removeChild(node);
+    return node;
+  }
+
+  return null;
+}