Helm

This draft keeps the useful part of a migration note intact: back up the old Uptime Kuma data, install the chart, restore the data into the new deployment, switch the service to LoadBalancer, and verify the endpoint from outside the cluster.

This draft captures the part of a Longhorn installation that usually matters most in practice: make sure the node dependencies are in place, enable iscsid, run the environment check script, fix the obvious blockers, and only then install the chart.