Release v2.12.0

[jvanderaa]

Tracking issue for the v2.12.0 minor release, following docs/dev/release_checklist.md.

Highlights

• Six new provider parsers: SummitIG, RETN, Telxius, Vodafone, Cirion (Lumen fork), FLAG (fka Globalcloudexchange)
• Python 3.14 added to the supported version range
• Security floors raised for shipped deps (lxml, urllib3, requests, pygments)

Checklist

• CI green on develop
• Version bumped to 2.12.0
• Release notes generated (version_2.12.md); fragments consumed
• Backfill version_2.11.md to restore the split-file pattern
• mkdocs.yml nav updated
• Release PR into main (merge commit, not squash)
• Tag v2.12.0 + publish GitHub Release (target main)
• PR main -> develop with poetry version prepatch
• Verify PyPI publish + ReadTheDocs build