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/cjs/hyphenateStyle.js

@@ -0,0 +1,21 @@
+"use strict";
+
+var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault");
+
+exports.__esModule = true;
+exports.default = hyphenateStyleName;
+
+var _hyphenate = _interopRequireDefault(require("./hyphenate"));
+
+/**
+ * Copyright 2013-2014, Facebook, Inc.
+ * All rights reserved.
+ * https://github.com/facebook/react/blob/2aeb8a2a6beb00617a4217f7f8284924fa2ad819/src/vendor/core/hyphenateStyleName.js
+ */
+var msPattern = /^ms-/;
+
+function hyphenateStyleName(string) {
+  return (0, _hyphenate.default)(string).replace(msPattern, '-ms-');
+}
+
+module.exports = exports["default"];