Clean up old branches monthly

[Matteo-it]

Adds a GitHub Action stale-branch-cleanup.yml that automatically removes stale remote branches. The repo has accumulated many old branches (stale, closed, already merged), and this workflow cleans them up safely.

What it does

• Runs automatically once a month (03:00 UTC, day 1) via schedule cron.
• Deletes remote branches whose last commit is older than 365 days.
• Can also be triggered manually via workflow_dispatch.

Safety

• Always skips the default branch and common protected names (main, master, develop, staging, production, gh-pages).
• Dry-run mode: manual runs default to a simulation that only lists candidate branches without deleting. Scheduled runs perform the actual deletion.
• Configurable days_threshold on manual runs.
• Uses only GITHUB_TOKEN with contents: write, no extra secrets.Adds a GitHub Action (stale-branch-cleanup.yml) that automatically removes stale remote branches. The repo has accumulated many old branches (stale, closed, already merged), and this workflow cleans them up safely.

[damianoc90]

Isn't this a bit too much? Branches older than 3 months are probably already stale.