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/hyphenate.js

@@ -0,0 +1,11 @@
+"use strict";
+
+exports.__esModule = true;
+exports.default = hyphenate;
+var rUpper = /([A-Z])/g;
+
+function hyphenate(string) {
+  return string.replace(rUpper, '-$1').toLowerCase();
+}
+
+module.exports = exports["default"];