Expose library_type_name in API and remove redundant empty fields

- Add library_type_name to GetMediaItem handler response in media.go
- Remove empty LibraryName and LibraryTypeName fields from:
  - ListMediaItemsRow in collections.go handler
  - ListMediaItemsRow in dashboard_service.go
- These fields are now populated at the database level via trigger

The library_type_name is now automatically populated in the database
when a media item is created, so we remove the manual empty string
assignments and expose the actual value in the API response.

internal/handlers/collections.go

@@ -1007,7 +1007,5 @@ func mediaItemsToListMediaItemsRow(item database.MediaItems) database.ListMediaI
 		OpfIdentifier:      item.OpfIdentifier,
 		OpfUuid:            item.OpfUuid,
 		HashConfidence:     item.HashConfidence,
-		LibraryName:        "",
-		LibraryTypeName:    "",
 	}
 }