Update @apollo/client to v4.0.0

[pylipp]

Background

• we use the @apollo/client library for working with GraphQL APis; defined in package.json

Task

• update it to the latest version v4.1.1
• make sure all builds work (pnpm -C front build and pnpm -C statviz build both pass)
• make sure all tests pass (pnpm test)
• use GPT-5 to solve this

[pylipp]

superceded by https://trello.com/c/I4BqskML