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/config/config.go

@@ -9,6 +9,7 @@ import (
 )
 
 type Config struct {
+	Language        string                `yaml:"language"`
 	Server          ServerConfig          `yaml:"server"`
 	DB              DBConfig              `yaml:"db"`
 	Logger          LoggerConfig          `yaml:"logger"`
@@ -21,6 +22,17 @@ type Config struct {
 	CustomerSession CustomerSessionConfig `yaml:"customerSession"`
 }
 
+func (c Config) LanguageOrDefault() string {
+	switch strings.ToLower(strings.TrimSpace(c.Language)) {
+	case "zh", "zh-cn", "zh_cn", "zh-hans":
+		return "zh-CN"
+	case "en", "en-us", "en_us":
+		return "en-US"
+	default:
+		return "zh-CN"
+	}
+}
+
 type WxWorkNotifyConfig struct {
 	Enabled                bool    `yaml:"enabled"`
 	ToUsers                []int64 `yaml:"toUsers"`