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/@babel/runtime/helpers/esm/initializerDefineProperty.js

@@ -0,0 +1,9 @@
+function _initializerDefineProperty(e, i, r, l) {
+  r && Object.defineProperty(e, i, {
+    enumerable: r.enumerable,
+    configurable: r.configurable,
+    writable: r.writable,
+    value: r.initializer ? r.initializer.call(l) : void 0
+  });
+}
+export { _initializerDefineProperty as default };