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/collectSiblings.js

@@ -0,0 +1,24 @@
+import matches from './matches';
+export default function collectSiblings(node, refNode, selector) {
+  if (refNode === void 0) {
+    refNode = null;
+  }
+
+  if (selector === void 0) {
+    selector = null;
+  }
+
+  var siblings = [];
+
+  for (; node; node = node.nextElementSibling) {
+    if (node !== refNode) {
+      if (selector && matches(node, selector)) {
+        break;
+      }
+
+      siblings.push(node);
+    }
+  }
+
+  return siblings;
+}