Add scheduled publish date UI for events

[trista-chen-29]

Changes

• Added frontend support for publish_date on SCEvents create/edit forms.
• Added scheduled event UI state for draft events with future publish dates.
• Display publish date metadata in admin event popups.
• Disable/clear publish date when an event is marked closed.

Testing

• Created a draft event with a future publish date and confirmed it appears on the admin calendar as Scheduled.

• Publish date is shown.

• Edited a scheduled event and confirmed the publish date loads and can be updated.

• Set an event to Closed and confirmed the publish date input is disabled/cleared.

• Confirmed the event was auto-published

[c1ndytat]

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