Add Korean translation (#439)

Co-authored-by: 송준우 <2484@coreit.co.kr>

src/ui/desktop/user/LanguageSwitcher.tsx

@@ -20,6 +20,7 @@ const languages = [
   },
   { code: "ru", name: "Russian", nativeName: "Русский" },
   { code: "fr", name: "French", nativeName: "Français" },
+  { code: "ko", name: "Korean", nativeName: "한국어" },
 ];
 
 export function LanguageSwitcher() {