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/supports-preserve-symlinks-flag/index.js

@@ -0,0 +1,9 @@
+'use strict';
+
+module.exports = (
+// node 12+
+	process.allowedNodeEnvironmentFlags && process.allowedNodeEnvironmentFlags.has('--preserve-symlinks')
+) || (
+// node v6.2 - v11
+	String(module.constructor._findPath).indexOf('preserveSymlinks') >= 0 // eslint-disable-line no-underscore-dangle
+);