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/vitest/dist/vendor/env.AtSIuHFg.js

@@ -0,0 +1,7 @@
+import 'std-env';
+
+var _a;
+const isNode = typeof process < "u" && typeof process.stdout < "u" && !((_a = process.versions) == null ? void 0 : _a.deno) && !globalThis.window;
+const isWindows = isNode && process.platform === "win32";
+
+export { isWindows as a, isNode as i };