Automate docs site version in `_config.yml` instead of hard-coding it

[aryasadeghi1]

Description

The documentation site version is hard-coded in docs/_config.yml:

# TODO: get version number from github
version: v4.6.1

It has to be manually bumped on every release, which is easy to forget and can leave the published docs showing a stale version. It is a separate step from the version.py / release bump, so the two can drift apart.

Proposal

Populate the docs version automatically instead of hard-coding it, e.g. read the latest GitHub release/tag (or reuse version.py) during the docs build, so docs/_config.yml no longer needs a manual edit per release.

Acceptance

• docs/_config.yml no longer requires a manual version: bump each release
• The published docs always show the current released version