test(staples): add empty categories edge case to StaplesManager

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/onboarding/StaplesManager.test.ts

@@ -99,4 +99,9 @@ describe('StaplesManager', () => {
 		const grid = screen.getByTestId('category-grid');
 		expect(grid.className).toContain('md:grid-cols-3');
 	});
+
+	it('renders without crashing when categories is empty', () => {
+		render(StaplesManager, { props: { categories: [], context: 'onboarding' } });
+		expect(screen.queryByRole('button')).not.toBeInTheDocument();
+	});
 });