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/lodash/_root.js

@@ -0,0 +1,9 @@
+var freeGlobal = require('./_freeGlobal');
+
+/** Detect free variable `self`. */
+var freeSelf = typeof self == 'object' && self && self.Object === Object && self;
+
+/** Used as a reference to the global object. */
+var root = freeGlobal || freeSelf || Function('return this')();
+
+module.exports = root;