Resolve "feat: Switch to cert manager"

General MR

Summary

Switching over to cert manager by default

Relevant logs/screenshots

n/a

Linked Issue

#383 (closed)

Upgrade Notices

Monitoring now uses the integrated cert-manager to issue and inject Prometheus Operator admission-webhook certificates by default. Ensure cert-manager is enabled and deployed before upgrading monitoring. Deployments previously using kube-webhook-certgen must either migrate to cert-manager or explicitly re-enable the supported patch method. The webhook uses Ignore only during initial installation and switches to Fail on upgrades once the webhook should be available. For more details see our migration doc.

Umbrella Branch

monitoring-383-switch-to-cert-manager