refs: https://github.com/TryGhost/Product/issues/3729
- Wired up the FirstPromoter api to adminx
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### <samp>🤖 Generated by Copilot at bacd8ec</samp>
This pull request refactors the `FirstPromoterModal` component to use
hooks and helper functions, and adds a new end-to-end test file to
verify its functionality. The purpose of these changes is to improve the
code quality and the user experience of the FirstPromoter integration
feature.
