refactor: upgrade ESLint 9→10 and simplify React lint toolchain

- Upgrade eslint and @eslint/js to v10
- Replace eslint-plugin-react-x + eslint-plugin-react-dom + eslint-plugin-react-hooks
  with unified @eslint-react/eslint-plugin
- Raise dev Node.js requirement to ^22.13.0 || >=24 (runtime packages unaffected)
- Add .npmrc with engine-strict=true
- Move all @eslint-react rule overrides to eslint.config.js,
  eliminating plugin-specific inline eslint-disable comments
- Fix real issues caught by new rules: useless assignments,
  leaked setTimeout, ref naming, useState setter naming

packages/website/src/i18n/context.tsx

@@ -9,19 +9,19 @@ const LanguageContext = createContext<{
 } | null>(null)
 
 export function LanguageProvider({ children }: { children: ReactNode }) {
-	const [language, setLang] = useState<Lang>(() => {
+	const [language, setLanguage] = useState<Lang>(() => {
 		const stored = localStorage.getItem('language') as Lang
 		if (stored === 'zh-CN' || stored === 'en-US') return stored
 		return navigator.language.startsWith('zh') ? 'zh-CN' : 'en-US'
 	})
 
-	const setLanguage = (lang: Lang) => {
-		setLang(lang)
+	const switchLanguage = (lang: Lang) => {
+		setLanguage(lang)
 		localStorage.setItem('language', lang)
 	}
 
 	return (
-		<LanguageContext value={{ language, isZh: language === 'zh-CN', setLanguage }}>
+		<LanguageContext value={{ language, isZh: language === 'zh-CN', setLanguage: switchLanguage }}>
 			{children}
 		</LanguageContext>
 	)