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/fastq/example.mjs

@@ -0,0 +1,9 @@
+import { promise as queueAsPromised } from './queue.js'
+
+const queue = queueAsPromised(worker, 1)
+
+console.log('the result is', await queue.push(42))
+
+async function worker (arg) {
+  return 42 * 2
+}