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/square-stack.js

@@ -0,0 +1,17 @@
+/**
+ * @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 SquareStack = createLucideIcon("SquareStack", [
+  ["path", { d: "M4 10c-1.1 0-2-.9-2-2V4c0-1.1.9-2 2-2h4c1.1 0 2 .9 2 2", key: "4i38lg" }],
+  ["path", { d: "M10 16c-1.1 0-2-.9-2-2v-4c0-1.1.9-2 2-2h4c1.1 0 2 .9 2 2", key: "mlte4a" }],
+  ["rect", { width: "8", height: "8", x: "14", y: "14", rx: "2", key: "1fa9i4" }]
+]);
+
+export { SquareStack as default };
+//# sourceMappingURL=square-stack.js.map