fix: Use specific checkbox selector in UnifiedAgents test

The test was using getByRole('checkbox') which now matches multiple
elements after adding the "Skip certificate verification" checkbox.
Use name matcher to select the specific Docker monitoring checkbox.

frontend-modern/src/components/Settings/__tests__/UnifiedAgents.test.tsx

@@ -386,7 +386,7 @@ describe('UnifiedAgents platform commands', () => {
     });
 
     // Docker monitoring is disabled by default
-    const checkbox = screen.getByRole('checkbox');
+    const checkbox = screen.getByRole('checkbox', { name: /Enable Docker monitoring/i });
     expect(checkbox).not.toBeChecked();
 
     // Enable it