[FEAT] Automatically mark abandoned issues and PRs as Stale

[github-actions]

Problem Statement

The repository can get cluttered with PRs where the contributor vanished after receiving review feedback.

Proposed Solution

Implement the official actions/stale workflow. Configure it to run once a day. If a PR has seen zero activity (comments or commits) for 30 days, it adds a stale label and comments a warning. If 7 more days pass with no response, it automatically closes the PR.

Alternatives Considered

N/A. actions/stale is the industry standard.

Additional Context

The configuration should go in .github/workflows/stale.yml.

[Aditya8369]

@PRODHOSH please assign me