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/lucide-react/dist/esm/icons/shield.js

@@ -0,0 +1,15 @@
+/**
+ * @license lucide-react v0.303.0 - ISC
+ *
+ * This source code is licensed under the ISC license.
+ * See the LICENSE file in the root directory of this source tree.
+ */
+
+import createLucideIcon from '../createLucideIcon.js';
+
+const Shield = createLucideIcon("Shield", [
+  ["path", { d: "M12 22s8-4 8-10V5l-8-3-8 3v7c0 6 8 10 8 10", key: "1irkt0" }]
+]);
+
+export { Shield as default };
+//# sourceMappingURL=shield.js.map