Add native cron task runner command to Quantum CLI (qt cron:run)

[armanist]

Introduce a new CLI command qt cron:run to enable running scheduled tasks inside Quantum projects with ease.

This feature will allow developers to define cron jobs as PHP files under a cron/ directory and run all due jobs with a single system cron entry calling php qt cron:run. The command will support cron expression parsing, task locking, and logging.

Acceptance Criteria:

• php qt cron:run executes and runs all due cron jobs.
• Tasks can be defined as PHP files with cron expression and callback.
• Locking prevents concurrent task runs.
• Errors in tasks are caught and reported.
• Composer dependency dragonmantank/cron-expression is added.
• Documentation updated with setup and usage guide.

Additional Notes:

System cron entry example:

* * * * * php qt cron:run >> /dev/null 2>&1