Fix: Remove unused imports (Check, X) in Header.tsx

frontend/src/components/Header.tsx

@@ -1,4 +1,4 @@
-import { Zap, Check, X, MessageSquare } from 'lucide-react';
+import { Zap, MessageSquare } from 'lucide-react';
 
 interface HeaderProps {
   isConnected: boolean;