fix: 修复订阅更新 group_locked 不能为 null 问题 + Kutt 短链3次重试

- updateUserSubscribeLogic: 更新订阅时补充 GroupLocked 字段，避免写入 NULL 触发数据库约束错误
- inviteLinkResolver: generateShortLinkWithTimeout 增加最多3次重试，防止网络波动导致短链生成失败

Co-Authored-By: claude-flow <ruv@ruv.net>

internal/logic/admin/user/updateUserSubscribeLogic.go

@@ -54,6 +54,7 @@ func (l *UpdateUserSubscribeLogic) UpdateUserSubscribe(req *types.UpdateUserSubs
 		UUID:        userSub.UUID,
 		Status:      userSub.Status,
 		NodeGroupId: userSub.NodeGroupId,
+		GroupLocked: userSub.GroupLocked,
 	})
 
 	if err != nil {

internal/logic/common/inviteLinkResolver.go

@@ -215,18 +215,26 @@ func (r *InviteLinkResolver) generateShortLinkWithTimeout(referCode string, time
 	}
 	_, domain := r.resolveShareURLAndDomain()
 
-	requestCtx := r.ctx
-	var cancel context.CancelFunc
-	if timeout > 0 {
-		requestCtx, cancel = context.WithTimeout(r.ctx, timeout)
-		defer cancel()
+	const maxRetries = 3
+	var lastErr error
+	for attempt := 0; attempt < maxRetries; attempt++ {
+		requestCtx := r.ctx
+		var cancel context.CancelFunc
+		if timeout > 0 {
+			requestCtx, cancel = context.WithTimeout(r.ctx, timeout)
+		}
+
+		shortLink, err := r.createShortLink(requestCtx, longLink, domain)
+		if cancel != nil {
+			cancel()
+		}
+		if err == nil && strings.TrimSpace(shortLink) != "" {
+			return strings.TrimSpace(shortLink), nil
+		}
+		lastErr = err
 	}
 
-	shortLink, err := r.createShortLink(requestCtx, longLink, domain)
-	if err != nil {
-		return "", err
-	}
-	return strings.TrimSpace(shortLink), nil
+	return "", lastErr
 }
 
 func (r *InviteLinkResolver) getCachedShortLink(referCode string) string {