Post in slack if any new contract upgrade approval is found on chain

## Done Criteria
`#foc-wg` is notified if an upgrade announcement is posted on chain including:
- network in question (calibnet, mainnet)
- min epoch for executing the epoch
- how many epochs / hours away that epoch is
- new contract address

This applies for both pdp-verifier and fwss.

## Why Important
Give visibility on contract updates to make sure nothing unintentional or malicious going on. Extra eyes on contract upgrades doesn't hurt.

## Notes
1. This came out of discussion in https://app.notion.com/p/filecoindev/202606-Contract-upgrade-delay-decision-FWSS-and-PDPVerifier-38bdc41950c18080be5bfe1179b53a81
2. foc-observer can apparently answer this easily - it just needs to be polled.
3. Maybe also post in `#fil-foc`?

No file, test, or entry point is named. Start by locating the repository's Python entry point and any existing polling or Slack-notification path, using the foc-observer note as the integration lead. Done means both pdp-verifier and fwss announcements notify #foc-wg with the network, execution epoch, time or epochs remaining, and new contract address.

Written by the indexing model from the issue text.