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/siginfo/test.js

@@ -0,0 +1,16 @@
+var siginfo = require('.')
+var pkg = require('./package.json')
+
+var stop = siginfo(function () {
+  console.dir({
+    version: pkg.version,
+    uptime: process.uptime()
+  })
+})
+
+process.stdout.resume()
+
+setTimeout(function () {
+  stop()
+  process.exit(0)
+}, 2000)