Read the caller company's supplier network graph

The caller company's graph: one layer per production process (highest position first), each with its nodes — company, facility processes and stored canvas position — and the links between shown nodes. filter is JSON { facilityProcesses?, name?, country? }: facility processes and name are case-insensitive substring matches, country an exact match, comma-separated values match any. Answers the { data, metadata } envelope (legacy answered the bare view). 404 graph_not_found when the company has no graph yet.