fix(editor): schedule publication behind an on/off toggle (no accidental date)
The "Publish on" date field was always open → an accidentally chosen date silently
set the post to 'scheduled' (not live, no obvious reason). Now a "Schedule
publication" toggle, off by default = publish immediately; the date field appears
and counts only when the toggle is on (input disabled when off). Server honours
publish_at only with schedule_enabled (bulletproof, create + update). NL/EN/DE.
Co-Authored-By: Claude <noreply@…>