feat: 邮箱规范化(NormalizeEmail)与域名白名单检查(IsEmailDomainWhitelisted)

internal/logic/public/user/emailTrialGrant.go

@@ -39,6 +39,16 @@ func tryGrantTrialOnEmailBind(ctx context.Context, svcCtx *svc.ServiceContext, l
 		return
 	}
 
+	// Cross-user check: prevent the same real inbox (via dot trick / + alias) from
+	// getting multiple trials across different accounts.
+	if auth.NormalizedEmailHasTrial(ctx, svcCtx.DB, email, rc.TrialSubscribe) {
+		log.Infow("normalized email already has trial via another account, skip",
+			logger.Field("email", email),
+			logger.Field("owner_user_id", ownerUserId),
+		)
+		return
+	}
+
 	sub, err := svcCtx.SubscribeModel.FindOne(ctx, rc.TrialSubscribe)
 	if err != nil {
 		log.Errorw("failed to find trial subscribe template", logger.Field("error", err.Error()))