Stable v2.6.39

• fix(firewall): drop unused helper + don't corrupt port ranges on edit
• fix(plesk-import): detect subdomains by name when parent_dom_id is absent
• docs(changelog): drop the custom-includes feat/revert noise
• feat(firewall): multiple ports per rule + block an IP on all ports
• fix(plesk-import): mailbox password 400 + false 'incomplete' on no-webhosting domains
• fix(ftp-tls): present the panel-host cert, not the first tenant's domain cert
• fix(multiserver): node onboarding inherits controller channel + auto-registers IPs
• fix(update): auto-align fleet version on channel switch (no more node drift)