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/codepen.js

@@ -0,0 +1,19 @@
+/**
+ * @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 Codepen = createLucideIcon("Codepen", [
+  ["polygon", { points: "12 2 22 8.5 22 15.5 12 22 2 15.5 2 8.5 12 2", key: "srzb37" }],
+  ["line", { x1: "12", x2: "12", y1: "22", y2: "15.5", key: "1t73f2" }],
+  ["polyline", { points: "22 8.5 12 15.5 2 8.5", key: "ajlxae" }],
+  ["polyline", { points: "2 15.5 12 8.5 22 15.5", key: "susrui" }],
+  ["line", { x1: "12", x2: "12", y1: "2", y2: "8.5", key: "2cldga" }]
+]);
+
+export { Codepen as default };
+//# sourceMappingURL=codepen.js.map