feat: Add webhook sender worker for delivering event notifications

[Dobrunia]

Summary

• Add a new sender/webhook worker that delivers event notifications as JSON POST requests to user-configured endpoint URLs
• Register Webhook in the ChannelType enum so the notifier dispatches webhook tasks automatically
• Add run-webhook script and docker-compose service

[codex-assistant]

Please add a PR description 🙂

Respect the reviewers — a description helps others understand the changes and review them faster. Keep it short, clear, and to the point. It also serves as documentation for future reference.

The PR was moved to Draft until a description is added.

[codex-assistant]

Please add a PR description 🙂

Respect the reviewers — a description helps others understand the changes and review them faster. Keep it short, clear, and to the point. It also serves as documentation for future reference.

The PR was moved to Draft until a description is added.

[codex-assistant]

Please add a PR description 🙂

Respect the reviewers — a description helps others understand the changes and review them faster. Keep it short, clear, and to the point. It also serves as documentation for future reference.

The PR was moved to Draft until a description is added.

[codex-assistant]

Please add a PR description 🙂

Respect the reviewers — a description helps others understand the changes and review them faster. Keep it short, clear, and to the point. It also serves as documentation for future reference.

The PR was moved to Draft until a description is added.

[codex-assistant]

Thanks for adding a description — the PR is now marked as Ready for Review.