fix: unify chinese language code as zh-CN

src/i18nLanguages.ts

@@ -1,7 +1,7 @@
 import type { Lang } from "./i18n";
 
 export const LANG_OPTIONS: { code: Lang; label: string }[] = [
-  { code: "zh", label: "中文" },
+  { code: "zh-CN", label: "中文" },
   { code: "en", label: "English" },
   { code: "ja", label: "日本語" },
   { code: "ko", label: "한국어" },
@@ -12,6 +12,7 @@ export const LANG_OPTIONS: { code: Lang; label: string }[] = [
 
 export function languageLabel(t: (key: string) => string, code: string) {
   if (!code) return t("filterLanguageAll");
-  const label = t(`lang_${code}`);
-  return label === `lang_${code}` ? code : label;
+  const key = `lang_${code.replace("-", "_")}`;
+  const label = t(key);
+  return label === key ? code : label;
 }