schema explorer: filter based on federation service name

In order to see which fields are unused within a service, filtering down the displayed types and fields based on a service name is a good addition.

We could put this filter next to the following elements:

<img width="458" height="214" alt="Image" src="https://github.com/user-attachments/assets/d3e85bef-bb06-4332-a074-0afbcdcaa879" />