Always load system blueprint for purging logs even if tutorial flows are disabled

[anna-geller]

Describe the issue

loading the purge flow should be independent of this configuration:

kestra:
  tutorial-flows:
    enabled: false # true by default

even if this is set to false, this blueprint should be loaded: https://kestra.io/blueprints/trigger/234-purge-execution-data-including-logs-metrics-and-outputs-on-a-schedule

[loicmathieu]

This needs to be discussed, see https://kestra-io.slack.com/archives/C04HTFM3VL6/p1727683936404919

[anna-geller]

Final next steps from Slack thread:

• on 0.19.0, display the system namespace even if no flow exists (@loicmathieu on it)
• on 0.20.0, find a way to load purge flow only for new instances and the trigger should be active

Why only for new instances? If this flow is loaded and the trigger is active, it removes past executions and logs older than 1 month without any warning which can lead to a usage spike on the instance database during the cleanup, small DBs could even crash.

Why this trigger is enabled? it's generally best practice to remove old logs and decision was made to keep it enabled for new instances.