CI/CD: Add a dedicated GitHub Action to label and manage stale issues

[rohan-pandeyy]

Description

While reviewing the current workflows under .github/workflows, I noticed that we don’t have any automation in place to handle inactive or long-running issues.

Current state

• There is no workflow that labels or closes stale issues.
• All existing workflows (for example, auto-issue-comment.yml, linked-issue.yml) are event-driven and run only when an issue or PR is updated.
• None of the workflows run on a scheduled basis, which is required to periodically scan for inactivity.

Because stale issue handling requires a time-based scan (for example, checking for issues inactive for 60+ days), extending an existing event-triggered workflow would make it harder to reason about and maintain.

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Proposal

Introduce a dedicated stale.yml workflow using a standard stale-bot approach.
This workflow would:

1. Run on a daily schedule (cron-based).
2. Label issues as stale after a configurable period of inactivity (I say 20 days).
3. Optionally post a comment notifying the user that the issue needs attention.
4. Automatically close the issue after a follow-up period (e.g., 7 days) if there is still no activity.
5. Exempt important labels (e.g., gsoc, proposal, bug, high-priority) if needed.

Many major OS organizations already make use of this action and PictoPy could profit from such an automated workflow.

[github-actions]

👋 Thanks for opening this issue! The maintainers will review it shortly. Till then, do not open any PR. This is a strict rule we like to follow around here :)

[SakshiGupta26]

Hi, this looks interesting. I would love to work on it once maintainers approve and allow contributions on this issue.