docs: add doc version for v1.12 and v2.5 fixes

[vdusek]

Summary

• Add versioned docs for v1.12 (latest 1.x) from git tag v1.12.2.
• Fix Python version requirement in v2.5 docs (3.11+ → 3.10+).
• Override DocsVersionDropdownNavbarItem so the version dropdown navigates to reference/<version> instead of docs/<version> when on API reference pages.
  • Same as in the JS version.

Known limitation

• SubNavbar links (Docs/Reference/Changelog) don't preserve the selected version — tracked in SubNavbar links don't preserve selected docs version #675.
  • This applies to JS repos (both client & SDK) as well.

Test plan

• Tested locally
• CI passes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.75%. Comparing base (5b57ff3) to head (a4dcf60).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #676   +/-   ##
=======================================
  Coverage   94.75%   94.75%           
=======================================
  Files          45       45           
  Lines        4404     4404           
=======================================
  Hits         4173     4173           
  Misses        231      231           

Flag	Coverage Δ
integration	94.75% <ø> (ø)

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[barjin]

Since the swizzled component is based on https://github.com/apify/apify-client-js/blob/master/website/src/theme/NavbarItem/DocsVersionDropdownNavbarItem.js, I don't have any other points.

As discussed through Slack, let's extract this to a common component in docs-theme eventually.