Refactor localization strings to English across various services and UI components

- Updated titles and subtitles in channel_service.go for web channel and WeChat MP channel configurations.
- Changed handoff messages in conversation_human_dispatch_service.go to English.
- Modified notification messages in event handlers for ticket and conversation assignments to English.
- Adjusted ticket creation messages in ticket_service.go to reflect English localization.
- Updated default locale settings in i18n configuration files to English (en-US).
- Changed HTML language attribute in layout.tsx to English.
- Refactored widget locale detection logic in agent-desk-sdk.ts to prioritize English.

web/lib/sdk/agent-desk-sdk.ts

@@ -42,9 +42,9 @@ function getWidgetLocale() {
   try {
     const stored = window.localStorage?.getItem("cs_ai_agent_locale")
     const language = stored || document.documentElement.lang || window.navigator?.language || ""
-    return language.toLowerCase().startsWith("en") ? "en-US" : "zh-CN"
+    return language.toLowerCase().startsWith("zh") ? "zh-CN" : "en-US"
   } catch {
-    return "zh-CN"
+    return "en-US"
   }
 }