Program items list: sorting options and scheduled/unscheduled indicator column

The program items list in Program V2 admin currently sorts by start time / creation time by default. When scheduling items, they jump around the list as they get scheduled, making it hard to track progress.

## Requested behaviour

1. **Default sort**: alphabetical by title
2. **Additional sort options**: by first schedule time, by creation time, by status
3. **Additional column**: first schedule time (or "Not scheduled" indicator), so the manager can see at a glance which items are scheduled and which are not without opening each one

## Background

Reported by Desucon Frostbite 2026 program management.