docs: update landing page stats and branch naming convention (#2727)

* docs: update landing page stats and branch naming convention

- Update community extensions: 91 → 105
- Update extension authors: 50+ → 60+
- Update presets: 18 → 22
- Update GitHub stars: 96K+ → 106K+
- Add last-updated date to landing page
- Clarify branch naming convention for PR-only changes

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

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Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>