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.

internal/services/conversation_human_dispatch_service_test.go

@@ -42,7 +42,7 @@ func TestConversationHumanDispatchAIHandoffOffHoursKeepsAIServingAndSendsNotice(
 	if message == nil {
 		t.Fatalf("expected off-hours notice message")
 	}
-	if message.SenderType != enums.IMSenderTypeAI || !strings.Contains(message.Content, "当前暂不在人工客服服务时间内") {
+	if message.SenderType != enums.IMSenderTypeAI || !strings.Contains(message.Content, "Human support is currently outside service hours") {
 		t.Fatalf("unexpected off-hours message: %+v", message)
 	}
 }