Extract the shouldRunNow() method from ScheduledJobManager and ServerManagerJob into
a reusable shouldRunCronNow() helper function. This centralizes cron scheduling logic
and enables consistent deduplication behavior across all scheduled job types.
- Create shouldRunCronNow() helper in bootstrap/helpers/shared.php with timezone
and dedup support
- Refactor ScheduledJobManager and ServerManagerJob to use the shared helper
- Add ScheduledJobDiagnostics command for inspecting cache state and scheduling
decisions across all scheduled jobs
- Simplify shouldRunNow tests to directly test the helper function
- Add DockerCleanupJob test for error handling and execution tracking
- Increase scheduled log retention from 1 to 7 days
