Add Clear All Data feature to settings page

- Add 'Clear All Data' button in Danger Zone section
- Implement confirmation dialog before clearing
- Clear all localStorage and redirect to onboarding
- Add translations for clearAllData, clearAllDataConfirm, and clearAllDataDescription in all 5 languages (EN, DE, FR, IT, PL)
- Style with red theme to indicate destructive action

src/app/settings/page.tsx

@@ -5,7 +5,7 @@ import { useRouter } from "next/navigation";
 import Header from "@/components/Header";
 import { useTranslation } from "@/lib/i18n/useTranslation";
 import { SupportedLanguage } from "@/lib/i18n/translations";
-import { ArrowLeft, Save } from "lucide-react";
+import { ArrowLeft, Save, Trash2 } from "lucide-react";
 
 export default function SettingsPage() {
     const router = useRouter();
@@ -58,6 +58,16 @@ export default function SettingsPage() {
         router.push("/");
     };
 
+    const handleClearAllData = () => {
+        if (window.confirm(t.common.clearAllDataConfirm)) {
+            // Clear all localStorage
+            localStorage.clear();
+
+            // Redirect to onboarding
+            router.push("/onboarding");
+        }
+    };
+
     if (!mounted) return null;
 
     return (
@@ -158,6 +168,23 @@ export default function SettingsPage() {
                                     </div>
                                 </div>
                             </div>
+
+                            {/* Danger Zone - Clear All Data */}
+                            <div className="pt-6 border-t border-red-200 dark:border-red-800">
+                                <h2 className="text-lg font-semibold text-red-600 dark:text-red-400 mb-2">
+                                    Danger Zone
+                                </h2>
+                                <p className="text-sm text-gray-600 dark:text-gray-400 mb-4">
+                                    {t.common.clearAllDataDescription}
+                                </p>
+                                <button
+                                    onClick={handleClearAllData}
+                                    className="flex items-center gap-2 px-4 py-2 bg-red-600 text-white rounded-lg hover:bg-red-700 font-medium shadow-md transition-all"
+                                >
+                                    <Trash2 size={18} />
+                                    {t.common.clearAllData}
+                                </button>
+                            </div>
                         </div>
 
                         <div className="pt-6 border-t border-gray-200 dark:border-gray-700 flex justify-end">

src/lib/i18n/translations.ts

@@ -9,6 +9,9 @@ export interface Translations {
         loading: string;
         error: string;
         save: string;
+        clearAllData: string;
+        clearAllDataConfirm: string;
+        clearAllDataDescription: string;
     };
 
     // Header
@@ -181,6 +184,9 @@ const en: Translations = {
         loading: 'Loading...',
         error: 'Error',
         save: 'Save',
+        clearAllData: 'Clear All Data',
+        clearAllDataConfirm: 'Are you sure you want to clear all data? This will delete all saved games, settings, and usernames. This action cannot be undone.',
+        clearAllDataDescription: 'Remove all saved games, settings, and cached data from your browser.',
     },
     header: {
         tagline: 'with Gemini & Stockfish',
@@ -342,6 +348,9 @@ const de: Translations = {
         loading: 'Lädt...',
         error: 'Fehler',
         save: 'Speichern',
+        clearAllData: 'Alle Daten löschen',
+        clearAllDataConfirm: 'Sind Sie sicher, dass Sie alle Daten löschen möchten? Dies löscht alle gespeicherten Spiele, Einstellungen und Benutzernamen. Diese Aktion kann nicht rückgängig gemacht werden.',
+        clearAllDataDescription: 'Alle gespeicherten Spiele, Einstellungen und zwischengespeicherten Daten aus Ihrem Browser entfernen.',
     },
     header: {
         tagline: 'mit Gemini & Stockfish',
@@ -503,6 +512,9 @@ const fr: Translations = {
         loading: 'Chargement...',
         error: 'Erreur',
         save: 'Enregistrer',
+        clearAllData: 'Effacer toutes les données',
+        clearAllDataConfirm: 'Êtes-vous sûr de vouloir effacer toutes les données ? Cela supprimera toutes les parties sauvegardées, les paramètres et les noms d\'utilisateur. Cette action est irréversible.',
+        clearAllDataDescription: 'Supprimer toutes les parties sauvegardées, les paramètres et les données en cache de votre navigateur.',
     },
     header: {
         tagline: 'avec Gemini & Stockfish',
@@ -664,6 +676,9 @@ const it: Translations = {
         loading: 'Caricamento...',
         error: 'Errore',
         save: 'Salva',
+        clearAllData: 'Cancella tutti i dati',
+        clearAllDataConfirm: 'Sei sicuro di voler cancellare tutti i dati? Questo eliminerà tutte le partite salvate, le impostazioni e i nomi utente. Questa azione non può essere annullata.',
+        clearAllDataDescription: 'Rimuovi tutte le partite salvate, le impostazioni e i dati memorizzati dal tuo browser.',
     },
     header: {
         tagline: 'con Gemini & Stockfish',
@@ -825,6 +840,9 @@ const pl: Translations = {
         loading: 'Ładowanie...',
         error: 'Błąd',
         save: 'Zapisz',
+        clearAllData: 'Wyczyść wszystkie dane',
+        clearAllDataConfirm: 'Czy na pewno chcesz wyczyścić wszystkie dane? Spowoduje to usunięcie wszystkich zapisanych gier, ustawień i nazw użytkowników. Ta akcja jest nieodwracalna.',
+        clearAllDataDescription: 'Usuń wszystkie zapisane gry, ustawienia i dane z pamięci podręcznej przeglądarki.',
     },
     header: {
         tagline: 'z Gemini i Stockfish',