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/postcss-selector-parser/dist/util/ensureObject.js

@@ -0,0 +1,17 @@
+"use strict";
+
+exports.__esModule = true;
+exports["default"] = ensureObject;
+function ensureObject(obj) {
+  for (var _len = arguments.length, props = new Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
+    props[_key - 1] = arguments[_key];
+  }
+  while (props.length > 0) {
+    var prop = props.shift();
+    if (!obj[prop]) {
+      obj[prop] = {};
+    }
+    obj = obj[prop];
+  }
+}
+module.exports = exports.default;