[Task] Introduce Sphinx-based API documentation and update docstrings

[Apricot-S]

Summary

The project currently does not use Sphinx for API documentation, and many existing docstrings are incomplete or inconsistent.
Some docstrings are already written in reST style, but not uniformly.
This task introduces Sphinx and updates docstrings across the codebase to support high‑quality API documentation for v2.

Scope

• Add Sphinx to the project and set up the initial documentation structure
• Update all public docstrings to follow the chosen style [Task] Update docstrings for the public API #121
• Ensure docstrings are complete, accurate, and suitable for Sphinx autodoc
• Generate API documentation pages using Sphinx
• Add a link to the generated documentation in the README, the Wiki and the pyproject.toml
• Confirm that the documentation builds cleanly and is readable