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.

internal/pkg/dto/response/auth_response.go

@@ -19,7 +19,8 @@ type LoginResponse struct {
 	Roles       []string          `json:"roles"`
 }
 
-type AuthOptionsResponse struct {
-	WxWorkEnabled bool `json:"wxworkEnabled"`
-	OIDCEnabled   bool `json:"oidcEnabled"`
+type PublicConfigResponse struct {
+	Language      string `json:"language"`
+	WxWorkEnabled bool   `json:"wxworkEnabled"`
+	OIDCEnabled   bool   `json:"oidcEnabled"`
 }