- Add docker_cleanup_old_images() to remove dangling images and keep only 2 most recent per tag
- Add docker_pull_with_marker() to pull images and update marker files tracking last pull time
- Add docker_setup_auto_pull_cronjob() to create/update system cronjob and wrapper script via hash-based detection
- Add docker_ensure_auto_pull_cronjob() to ensure cronjob is installed and up-to-date
- Create self-contained wrapper script at /usr/local/bin/armbian-docker-pull for cron execution
- Store configuration hash in /var/lib/armbian/docker-pull.hash for smart update detection
- Install cronjob at /etc/cron.d/armbian-docker-pull to pull images every 12 hours
- Move cronjob setup from docker_cli_prepare() to requirements command
- Cronjob is now only installed when users explicitly run ./compile.sh requirements
- Prevents "12 hours since last pull, pulling again" delay during builds
Signed-off-by: Igor Pecovnik <igor@armbian.com>
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