Add a retention timer for podcast

Jellyfin.Plugin.Jellypod/Api/JellypodController.cs

@@ -180,6 +180,11 @@ public class JellypodController : ControllerBase
             podcast.MaxEpisodesToKeep = request.MaxEpisodesToKeep.Value;
         }
 
+        if (request.MaxEpisodeAgeDays.HasValue)
+        {
+            podcast.MaxEpisodeAgeDays = request.MaxEpisodeAgeDays.Value;
+        }
+
         await _storageService.UpdatePodcastAsync(podcast).ConfigureAwait(false);
         return Ok(podcast);
     }

Jellyfin.Plugin.Jellypod/Api/Models/UpdatePodcastRequest.cs

@@ -14,4 +14,9 @@ public class UpdatePodcastRequest
     /// Gets or sets the maximum episodes to keep.
     /// </summary>
     public int? MaxEpisodesToKeep { get; set; }
+
+    /// <summary>
+    /// Gets or sets the maximum age in days for episodes (0 = use global, -1 = unlimited).
+    /// </summary>
+    public int? MaxEpisodeAgeDays { get; set; }
 }