Support contact creation via QueueWorker

Problem/Motivation

Currently, the Brevo module does not provide an asynchronous way to create contacts in Brevo.

We need a queue-based solution to handle contact creation reliably and asynchronously.

Proposed resolution

• Introduce a QueueWorker (brevo_create_contact) to handle contact creation asynchronously.
• Push new contacts to the queue instead of calling the API directly.
• The QueueWorker will consume the queue items and create the contacts using the Brevo API in the background.

Remaining tasks

User interface changes

API changes

• CreateContactQueue::processItem() now handles the creation of CreateContact items from the queue.

Data model changes

• No database schema changes.
• Queue items contain the contact data array, which is processed by the QueueWorker.