S3 storages with a self-signed or private CA certificate failed with
"cURL error 60", because the Coolify container and the backup helper do
not use the CA certificates of the host. The new opt-in setting turns off
the certificate check in the PHP S3 clients and sets MC_INSECURE for mc.
Closes#9762
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>