bug(cli-eest): `AppConfig.version` queries github.com

Currently doing `AppConfig.version` queries github.com to obtain information about the release.

It is not common practice on any software to rely on a third party server to tell it what its own version is. We need to have this locally.

This result in us (understandably) getting rate-limited during our unit tests: https://github.com/ethereum/execution-specs/actions/runs/30291952620/job/90063736783

Start at the Python implementation of AppConfig.version and inspect the unit tests that exercise it. Trace why the property contacts github.com, then verify that version lookup works locally without a network request and that the affected unit tests no longer trigger rate limiting.

Written by the indexing model from the issue text.