Create re-rendering tests that run in CI

[franknoirot]

Use a tool like react-scan and combine with Playwright and Vitest to assert that components do not excessively re-render (or re-render exactly as many times as we expect) during user flows. Up for discussion, but I believe this should be woven through existing tests using our fixtures to allow parts of the app to assert how many times they have re-rendered at various points during the user flows already under test.