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/@jridgewell/trace-mapping/src/strip-filename.ts

@@ -0,0 +1,8 @@
+/**
+ * Removes everything after the last "/", but leaves the slash.
+ */
+export default function stripFilename(path: string | undefined | null): string {
+  if (!path) return '';
+  const index = path.lastIndexOf('/');
+  return path.slice(0, index + 1);
+}