Complete LinkedChildren integration and batch DTO optimizations

This commit integrates remaining performance changes:

- Add batch user data fetching in DtoService to reduce N+1 queries
- Add GetNextUpEpisodesBatch in TVSeriesManager for efficient batch retrieval
- Update Video/Movie/BoxSet to use LibraryManager for alternate versions
- Transition LinkedChild to use ItemId instead of Path (obsolete Path/LibraryItemId)
- Update providers and controllers for LinkedChildren-based references
- Add NextUpEpisodeBatchResult for batched episode queries
- Integrate IDescendantQueryProvider in SqliteDatabaseProvider

1 files changed, 4 insertions, 1 deletions

diff --git a/MediaBrowser.LocalMetadata/Parsers/BaseItemXmlParser.cs b/MediaBrowser.LocalMetadata/Parsers/BaseItemXmlParser.cs
index 119effe791..cf1423d02d 100644
--- a/MediaBrowser.LocalMetadata/Parsers/BaseItemXmlParser.cs
+++ b/MediaBrowser.LocalMetadata/Parsers/BaseItemXmlParser.cs
@@ -780,7 +780,8 @@ namespace MediaBrowser.LocalMetadata.Parsers
         }
 
         /// <summary>
-        /// Get linked child.
+        /// Get linked child from XML. Uses deprecated Path/LibraryItemId properties for backward compatibility
+        /// with existing XML files. These will be resolved to ItemId when the linked child is accessed.
         /// </summary>
         /// <param name="reader">The xml reader.</param>
         /// <returns>The linked child.</returns>
@@ -791,6 +792,7 @@ namespace MediaBrowser.LocalMetadata.Parsers
             reader.MoveToContent();
             reader.Read();
 
+#pragma warning disable CS0618 // Type or member is obsolete - reading legacy XML format for backward compatibility
             // Loop through each element
             while (!reader.EOF && reader.ReadState == ReadState.Interactive)
             {
@@ -820,6 +822,7 @@ namespace MediaBrowser.LocalMetadata.Parsers
             {
                 return linkedItem;
             }
+#pragma warning restore CS0618
 
             return null;
         }