Add Polish UI language support

src/app/onboarding/page.tsx

@@ -133,7 +133,7 @@ export default function OnboardingPage() {
                             <div className="space-y-6">
                                 <p className="text-gray-700 dark:text-gray-300">{t.onboarding.language.description}</p>
                                 <div className="flex flex-wrap gap-3">
-                                    {["en", "de", "fr", "it"].map((lang) => (
+                                    {["en", "de", "fr", "it", "pl"].map((lang) => (
                                         <button
                                             key={lang}
                                             onClick={() => setLanguage(lang as SupportedLanguage)}

src/app/settings/page.tsx

@@ -85,7 +85,7 @@ export default function SettingsPage() {
                                     {t.start.language}
                                 </label>
                                 <div className="flex gap-3">
-                                    {(['en', 'de', 'fr', 'it'] as SupportedLanguage[]).map((lang) => (
+                                    {(['en', 'de', 'fr', 'it', 'pl'] as SupportedLanguage[]).map((lang) => (
                                         <button
                                             key={lang}
                                             onClick={() => setLanguage(lang)}