Iceberg Tracker: add duration as alert condition + notify when canceled/pulled

Right now the only alert filter on Iceberg Tracker (MBO) is total contracts executed. That’s not enough.

Icebergs that actually matter are usually the ones that stay on the book for a while, not just the ones with big size. A 30-contract iceberg that’s been sitting there for 20+ minutes is often more important than a huge one that only lasted 30 seconds.

I’d like to be able to set alerts like:

“Alert me when an iceberg hits at least 30 executed contracts and has been on the book for more than 20 minutes.”

Also useful: once an iceberg matches my filter, get notified when it gets canceled or fully traded.

These two things would make the alerts a lot more practical.