Add `CLAUDE.md`

## Description

Add a `CLAUDE.md` file to this repository to provide repository-specific context and guidance when working with Claude Code.

The structure and expected content for `CLAUDE.md` are being defined in insightsengineering/nestdevs-tasks#121. The implementation should follow the agreed structure from that issue and adapt the content to this repository.

The `CLAUDE.md` should capture the relevant repository-specific information while following the common conventions agreed for the teal repositories.

## Acceptance criteria

* `CLAUDE.md` is added to the repository.
* The file follows the structure agreed in insightsengineering/nestdevs-tasks#121.
* Repository-specific guidance is included where relevant.

Read insightsengineering/nestdevs-tasks#121 first to identify the agreed CLAUDE.md structure and conventions. Then inspect this repository's existing documentation and development guidance before creating CLAUDE.md. Done means the file exists at the repository root, follows that structure, and contains relevant teal-specific guidance.

Written by the indexing model from the issue text.