feat: auto-update events page from meetup issues via workflow dispatch

[Copilot]

The events page (website/events.md) was maintained manually. This adds a workflow_dispatch-triggered workflow so meetup planning repos in the org can push event data (date, title, hosting, meetup link) directly into the page.

Changes

• .github/workflows/update-events.yml — Accepts date, title, hosting, link inputs; runs the update script and commits to main, triggering the existing release.yml redeploy.

• .github/scripts/update-events.py — Patches website/events.md:

  • Validates date via datetime.strptime (rejects semantic invalids like 2026-02-31)
  • On first run, migrates existing 3-column table (Mois | Date cible | Lieu) to 4-column (Mois | Date | Titre | Lieu), preserving existing hosting data with empty title cells
  • Updates in-place if the month row already exists; otherwise inserts in sorted month order
  • Creates a new year section (descending order) when the year is not yet present

Example dispatch payload

# Called from a meetups repo workflow after issue validation:
uses: cloud-native-aixmarseille/.github/.github/workflows/update-events.yml@main
with:
  date: "2026-05-21"
  title: "eBPF en production"
  hosting: "Inria (Sophia)"
  link: "https://www.meetup.com/cloud-native-aix-marseille/events/313939118"