Function kind_from_jellyfin 

pub fn kind_from_jellyfin(item_type: &str, is_folder: bool) -> MediaKind

Classify a Jellyfin Type string into a neutral MediaKind.

Total and panic-free: any unrecognised string maps to MediaKind::Other rather than failing. is_folder disambiguates the one Jellyfin type (ChannelFolderItem) whose kind depends on whether it is a container.

The recognised set is every item_type the frontend audit found in use (docs/specs/frontend-domain-model.md), plus the common cast/crew person subtypes Jellyfin returns in People[].Type.