auto clean /var/lib/grafana/png/

[rschitz]

https://grafana.com/docs/grafana/latest/alerting/configure-notifications/template-notifications/images-in-notifications/

Grafana does not delete screenshots uploaded to its internal web server. To delete screenshots from static_root_path/images/attachments after a certain amount of time we recommend setting up a CRON job.

Contrary to https://github.com/grafana/grafana/blob/main/conf/defaults.ini#L18

Temporary files in data directory older than given duration will be removed
temp_data_lifetime = 24h