Description
This PR adds support for scheduling queue jobs using the queue() method.

It also introduces compatibility with the singleInstance() option, allowing job locking behavior to prevent duplicate job runs. The lock is applied when the job is queued and remains until the job is completed, with an optional TTL to manage job locking time. The details are described in the updated documentation.

This feature requires corresponding changes in the queue package to function properly: codeigniter4/queue#60

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide