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/object.assign/index.js

@@ -0,0 +1,22 @@
+'use strict';
+
+var defineProperties = require('define-properties');
+var callBind = require('call-bind');
+
+var implementation = require('./implementation');
+var getPolyfill = require('./polyfill');
+var shim = require('./shim');
+
+var polyfill = callBind.apply(getPolyfill());
+// eslint-disable-next-line no-unused-vars
+var bound = function assign(target, source1) {
+	return polyfill(Object, arguments);
+};
+
+defineProperties(bound, {
+	getPolyfill: getPolyfill,
+	implementation: implementation,
+	shim: shim
+});
+
+module.exports = bound;