Function cron_calc 

pub fn cron_calc(query: &str) -> String

Explain and compute next run times for cron expressions — offline, instant.

Standard 5-field cron: minute hour day-of-month month day-of-week Each field supports: *, */step, n, n,m, n-m, n-m/step

Commands: explain <expr> — plain-English description next <expr> — next 5 run times from now next N <expr> — next N run times bare <expr> — explain + next 5 runs