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/autoprefixer/lib/hacks/flex-spec.js

@@ -0,0 +1,19 @@
+/**
+ * Return flexbox spec versions by prefix
+ */
+module.exports = function (prefix) {
+  let spec
+  if (prefix === '-webkit- 2009' || prefix === '-moz-') {
+    spec = 2009
+  } else if (prefix === '-ms-') {
+    spec = 2012
+  } else if (prefix === '-webkit-') {
+    spec = 'final'
+  }
+
+  if (prefix === '-webkit- 2009') {
+    prefix = '-webkit-'
+  }
+
+  return [spec, prefix]
+}