fix: dark mode no admin, links mensagens dashboard, WhatsApp correto - Adicionado botão de dark mode no header do painel admin - Corrigido links do dashboard: /admin/contatos -> /admin/mensagens - Corrigido número WhatsApp: 5535988229445 (formato correto BR)

frontend/src/app/admin/layout.tsx

@@ -5,6 +5,7 @@ import Link from 'next/link';
 import { usePathname, useRouter } from 'next/navigation';
 import { useToast } from '@/contexts/ToastContext';
 import { useConfirm } from '@/contexts/ConfirmContext';
+import { useTheme } from 'next-themes';
 
 type TranslationSummary = {
   slug: string;
@@ -22,10 +23,12 @@ export default function AdminLayout({
   const [isLoading, setIsLoading] = useState(true);
   const [showAvatarModal, setShowAvatarModal] = useState(false);
   const [isUploading, setIsUploading] = useState(false);
+  const [mounted, setMounted] = useState(false);
   const pathname = usePathname();
   const router = useRouter();
   const { success, error } = useToast();
   const { confirm } = useConfirm();
+  const { theme, setTheme } = useTheme();
   const [showNotifications, setShowNotifications] = useState(false);
   const [translationSummary, setTranslationSummary] = useState<TranslationSummary[]>([]);
   const [isFetchingTranslations, setIsFetchingTranslations] = useState(false);
@@ -80,6 +83,7 @@ export default function AdminLayout({
   }, [success]);
 
   useEffect(() => {
+    setMounted(true);
     const fetchUser = async () => {
       try {
         const response = await fetch('/api/auth/me');
@@ -284,6 +288,19 @@ export default function AdminLayout({
           </button>
 
           <div className="flex items-center gap-4">
+            {/* Dark Mode Toggle */}
+            <button 
+              onClick={() => setTheme(theme === 'dark' ? 'light' : 'dark')}
+              className="w-10 h-10 rounded-lg hover:bg-gray-100 dark:hover:bg-white/5 flex items-center justify-center text-gray-600 dark:text-yellow-400 transition-colors cursor-pointer"
+              aria-label="Alternar tema"
+            >
+              {mounted && theme === 'dark' ? (
+                <i className="ri-sun-line text-xl"></i>
+              ) : (
+                <i className="ri-moon-line text-xl"></i>
+              )}
+            </button>
+
             <div ref={notificationsRef} className="relative">
               <button
                 onClick={() => {