Improve accessibility: wrap logo in div not H1

[hugovk]

Description

• Improve accessibility
• Screen readers often allow to easily jump from heading to heading
• It's preferred to only have a single H1 per page, and to maintain a hierarchy of headers
• The logo doesn't need to be an H1
• We already have other H1s (on release pages, it's "Python 3.14.2" (some pages have yet other H1s, that's another issue)
• https://www.w3.org/WAI/tutorials/page-structure/headings/
• https://www.a11yproject.com/posts/how-to-accessible-heading-structure/

This does move the logo/menu a couple of pixels up, but I don't think that matters, and better to improve the page semantics.

Before

After