refactor: remove LocaleSwitcher component and update locale handling

- Removed LocaleSwitcher from NavUser, SiteHeader, and WorkbenchHeader components.
- Updated tests to reflect the removal of LocaleSwitcher.
- Changed default locale from "en-US" to "zh-CN" in i18n configuration.
- Refactored locale resolution logic to read configured locale without relying on browser language detection.
- Updated AgentDesk SDK to support language configuration from public API.
- Cleaned up unused auth options fetching in the auth API.

web/i18n/config.ts

@@ -1,8 +1,7 @@
 export const SUPPORTED_LOCALES = ["zh-CN", "en-US"] as const
 export type AppLocale = (typeof SUPPORTED_LOCALES)[number]
 
-export const DEFAULT_LOCALE: AppLocale = "en-US"
-export const LOCALE_STORAGE_KEY = "cs_ai_agent_locale"
+export const DEFAULT_LOCALE: AppLocale = "zh-CN"
 
 const LOCALE_ALIASES: Record<string, AppLocale> = {
   zh: "zh-CN",
@@ -37,40 +36,13 @@ export function isSupportedLocale(
   return SUPPORTED_LOCALES.includes(value as AppLocale)
 }
 
-export function resolveBrowserLocale({
-  storedLocale,
-  navigatorLanguages,
-}: {
-  storedLocale?: string | null
-  navigatorLanguages?: readonly string[] | null
-}): AppLocale {
-  if (isSupportedLocale(storedLocale)) {
-    return storedLocale
-  }
-
-  for (const locale of navigatorLanguages ?? []) {
-    const normalized = normalizeSupportedLocale(locale)
-    if (normalized) {
-      return normalized
-    }
-  }
-
-  return DEFAULT_LOCALE
-}
+let configuredLocale: AppLocale = DEFAULT_LOCALE
 
 export function readStoredLocale(): AppLocale {
-  if (typeof window === "undefined") {
-    return DEFAULT_LOCALE
-  }
-  return resolveBrowserLocale({
-    storedLocale: window.localStorage.getItem(LOCALE_STORAGE_KEY),
-    navigatorLanguages: window.navigator.languages,
-  })
+  return configuredLocale
 }
 
-export function writeStoredLocale(locale: AppLocale) {
-  if (typeof window === "undefined") {
-    return
-  }
-  window.localStorage.setItem(LOCALE_STORAGE_KEY, locale)
+export function configureLocale(locale: string | null | undefined): AppLocale {
+  configuredLocale = normalizeLocale(locale)
+  return configuredLocale
 }