Summary

The French docs/setup section is not aligned with the upstream English documentation structure.
This issue focuses on aligning the directory structure and removing deprecated sections.

• Update _index.md to match upstream "Getting Started" structure
• Remove deprecated sections: custom-cloud/ & release/ which are no longer present in EN.

Goal

Ensure that content/fr/docs/setup matches the structure and navigation of content/en/docs/setup.

Part of the broader French documentation synchronization effort: #55609