feat(docs): serve werf 3 documentation as the latest version

[alexey-igrychev]

Summary

Make werf v3 the current documentation version on the website while preserving explicit access to v2 and v1.2.

What

• Route /docs/ and /docs/latest/ to v3 documentation and point the English and Russian Documentation menus at /docs/v3/.
• Scope documentation search to v3 on v3/latest/preview pages, retaining the v2 and v1.2 scopes on their versioned pages.
• Keep /docs/v2/ and /docs/v1.2/ available through the existing version routing.
• Allow crawlers to index v3 and list its sitemap, while preserving v2 indexing and its sitemap.
• Match production routing in the local documentation proxy and backend configuration.

Why

werf v3 is moving to the main development branch. The website must use the same default documentation version instead of continuing to direct readers and search engines to v2.

[alexey-igrychev]

Verification

• task site:check-docs-roots passes: production Helm renders for both clusters, current/supported backend roots, root/latest rewrites, local proxy/backend settings, navigation, robots and sitemaps.
• The JavaScript check executes the real version-group function for latest, v3, v2, v1.2, previews and non-docs URLs.
• Mutation checks reject restoring v2 as current, dropping v2 support, disabling latest, reverting JavaScript defaults or local backend configuration, and removing the v3 navigation/crawler/sitemap entries.
• Independent review traced latest through the backend to its X-Accel-Redirect and approved the final diff.

Follow-up

• Merge only after v3 werf#7377 is merged and the v3 production docs deployment is healthy.
• Verify live English/Russian root/latest/v2 routes after deployment.

[alexey-igrychev]

Added Podman and netavark to the spell-check dictionary (scripts/docs/spelling/wordlist and the generated scripts/docs/spelling/dictionaries/dev_OPS.dic). Both are proper names used in the v3 documentation; the spell check rejected them, which also fails on main and on the pre-existing baseline run, so this is not introduced by the routing change.

Note: task site:generate-special-dictionary regenerates the dictionary strictly from the wordlist, and the committed dictionary contained one extra entry (CRDs) that is not in the wordlist. That entry is preserved here so the change stays limited to the two new words.