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/binary-extensions/index.d.ts

@@ -0,0 +1,14 @@
+/**
+List of binary file extensions.
+
+@example
+```
+import binaryExtensions = require('binary-extensions');
+
+console.log(binaryExtensions);
+//=> ['3ds', '3g2', …]
+```
+*/
+declare const binaryExtensions: readonly string[];
+
+export = binaryExtensions;