gateway api fixes

src/EntKube.Web/Data/CnpgCluster.cs

@@ -77,6 +77,12 @@ public class CnpgCluster
     /// </summary>
     public string? BackupSchedule { get; set; }
 
+    /// <summary>
+    /// Number of days to retain backups. The Barman Cloud Plugin uses this as the
+    /// recovery window (e.g. "30d"). Expired backups are cleaned up automatically.
+    /// </summary>
+    public int RetentionDays { get; set; } = 30;
+
     /// <summary>
     /// Current lifecycle status of the cluster.
     /// </summary>