fix(client): normalize settings language selection

Author: ZengLiangYi

client/src/i18n/language.ts

@@ -0,0 +1,10 @@
+export const LANGUAGE_OPTIONS = ["zh", "en"] as const;
+
+export type LanguageOptionCode = (typeof LANGUAGE_OPTIONS)[number];
+
+export function getSelectedLanguageCode(
+	language: string | undefined,
+): LanguageOptionCode | undefined {
+	const baseLanguage = language?.split(/[-_]/, 1)[0]?.toLowerCase();
+	return LANGUAGE_OPTIONS.find((code) => baseLanguage === code);
+}

client/src/pages/SettingsPage.tsx

@@ -12,6 +12,10 @@ import {
 import { useEffect, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { ConfirmDialog } from "@/components/ConfirmDialog.tsx";
+import {
+	getSelectedLanguageCode,
+	LANGUAGE_OPTIONS,
+} from "@/i18n/language.ts";
 import { api } from "@/lib/api.ts";
 import { useTheme } from "@/providers/useTheme.ts";
 
@@ -137,10 +141,13 @@ export function SettingsPage() {
 		setPendingConfig(null);
 	};
 
-	const languages = [
-		{ code: "zh", label: t("language_name.zh") },
-		{ code: "en", label: t("language_name.en") },
-	];
+	const selectedLanguage = getSelectedLanguageCode(
+		i18n.resolvedLanguage ?? i18n.language,
+	);
+	const languages = LANGUAGE_OPTIONS.map((code) => ({
+		code,
+		label: t(`language_name.${code}`),
+	}));
 
 	return (
 		<div className="p-6 max-w-2xl">
@@ -193,7 +200,7 @@ export function SettingsPage() {
 							key={code}
 							onClick={() => i18n.changeLanguage(code)}
 							className={`px-4 py-2 text-sm border transition-colors ${
-								i18n.language === code
+								selectedLanguage === code
 									? "border-[var(--accent)] text-accent"
 									: "border-theme text-secondary hover:text-primary"
 							}`}

client/test/language.test.ts

@@ -0,0 +1,8 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { getSelectedLanguageCode } from "../src/i18n/language.ts";
+
+test("getSelectedLanguageCode maps regional browser language codes to base options", () => {
+	assert.equal(getSelectedLanguageCode("zh-CN"), "zh");
+	assert.equal(getSelectedLanguageCode("en-US"), "en");
+});