Add is_trakt_group field to PlaylistGroup and update sorting logic

- Introduced `is_trakt_group` field in `PlaylistGroup` struct to differentiate between Trakt and non-Trakt groups.
- Updated relevant parsing functions in `m3u.rs`, `xtream.rs`, and `trakt.rs` to set this field appropriately.
- Enhanced sorting logic in `sort.rs` to prioritize Trakt groups during playlist sorting.
- Ensured backward compatibility by defaulting `is_trakt_group` to false where applicable.

backend/src/processing/processor/playlist.rs

@@ -55,6 +55,7 @@ fn filter_playlist(playlist: &mut [PlaylistGroup], target: &ConfigTarget) -> Opt
                 title: pg.title.clone(),
                 channels,
                 xtream_cluster: pg.xtream_cluster,
+                is_trakt_group: pg.is_trakt_group,
             });
         }
     }
@@ -175,6 +176,7 @@ fn map_playlist(playlist: &mut [PlaylistGroup], target: &ConfigTarget) -> Option
                         title: title.to_string(),
                         channels: vec![channel.clone()],
                         xtream_cluster: *cluster,
+                        is_trakt_group: false,
                     });
                 }
             }