ci: trigger Meetup sync on PRs and all pushes to main

[carloshvp]

Motivation

• Ensure the Sync Meetup events workflow runs after every pull request targeting main/master and on all pushes to those branches because the previous push.paths filter prevented runs after most PRs.
• Avoid attempts to push changes back from runs triggered by PRs by skipping the commit step for pull_request events.

Description

• Added a pull_request trigger for main/master and removed the push.paths filter so the workflow runs on all pushes to those branches and on PRs targeting them in sync-meetup-events.yml.
• Guarded the commit step with if: github.event_name == 'push' || github.event_name == 'schedule' || github.event_name == 'workflow_dispatch' so commits/pushes only occur on non-PR runs.
• Left the sync logic in scripts/sync_meetup_events.py and the event output _data/events.json handling unchanged.

Testing

• Reviewed the workflow diff and verified the updated triggers and the commit-step conditional in sync-meetup-events.yml.
• Attempted to parse the workflow YAML using Python PyYAML, but parsing failed because PyYAML is not installed in the environment.
• Confirmed the updated workflow file is present in the repository and reflects the intended changes.

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Codex Task