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/loupe/lib/map.js

@@ -0,0 +1,27 @@
+import { inspectList } from './helpers'
+
+function inspectMapEntry([key, value], options) {
+  options.truncate -= 4
+  key = options.inspect(key, options)
+  options.truncate -= key.length
+  value = options.inspect(value, options)
+  return `${key} => ${value}`
+}
+
+// IE11 doesn't support `map.entries()`
+function mapToEntries(map) {
+  const entries = []
+  map.forEach((value, key) => {
+    entries.push([key, value])
+  })
+  return entries
+}
+
+export default function inspectMap(map, options) {
+  const size = map.size - 1
+  if (size <= 0) {
+    return 'Map{}'
+  }
+  options.truncate -= 7
+  return `Map{ ${inspectList(mapToEntries(map), options, inspectMapEntry)} }`
+}