ci: add stale issue/PR cleanup workflow

[Rome-1]

What

Add a GitHub Actions workflow to flag and eventually close stale issues and PRs.

Why

As the repo grows with community issues, stale items accumulate and make it harder to find active work. Standard OSS hygiene.

Suggested config

• Issues with no activity for 60 days get labeled `stale`
• Stale issues with no activity for 14 more days get closed
• PRs with no activity for 30 days get labeled `stale`
• Issues labeled `pinned` or `security` are exempt
• Stale label is removed on any new activity

File to create

`.github/workflows/stale.yml` — use `actions/stale@v9`

Reference

https://github.com/actions/stale

[kietcoderlor]

Hi! I’d like to work on this issue as part of my CodePath AI Open Source Capstone.

I plan to add the .github/workflows/stale.yml workflow using actions/stale@v9 and follow the stale/close behavior described in the issue.

Please let me know if there are any repo-specific workflow conventions I should follow.