feat(feedback): show the sender's interface language and connector bot in admin

In the console feedback detail, show the sender's interface language (account
preferred_language) always, and — for a message that arrived through an external
connector (currently Telegram) — the bot they last used (en/ru, from the
account's service_language).

backend/internal/server/handlers_admin_feedback.go

@@ -87,6 +87,14 @@ func (s *Server) consoleFeedbackDetail(c *gin.Context) {
 	if banned, err := s.accounts.HasRole(ctx, m.AccountID, account.RoleFeedbackBanned); err == nil {
 		view.Banned = banned
 	}
+	if acc, err := s.accounts.GetByID(ctx, m.AccountID); err == nil {
+		view.InterfaceLanguage = acc.PreferredLanguage
+		// The connector bot (the account's last service-language bot) is meaningful only
+		// for a message that arrived through an external connector — currently Telegram.
+		if m.Channel == "telegram" && acc.ServiceLanguage != "" {
+			view.BotLanguage = acc.ServiceLanguage
+		}
+	}
 	s.renderConsole(c, "feedback_detail", "feedback", "Feedback", view)
 }