Cardano Updates

* from docker-compose demo containers
* from nix process-compose demo commands

* this starts grafana and prometheus from docker-compose

> as is already present in its env field

* unset workaround env variable to avoid affecting other specs.

* adapt spec for ChainBackend

Signed-off-by: Sasha Bogicevic <[email protected]>

After rotation, we now reset the number of events to 1 (not 0),
because the checkpoint event is sourced on restart. This avoids
a mismatch between the rotation check on startup and during normal operation.

To support this, we changed the rotation condition to use (>) instead of (>=),
preventing an infinite rotation loop when the configured threshold is 1
(since checkpointing would otherwise immediately trigger a new rotation).

Lastly, the checkpoint event id now matches the last persisted event id
from the last rotated log file, preserving the sequential order
of event ids across logs.

This also makes it easier to identify the last rotated log file from a checkpoint,
as the checkpoint event id matches the log file name suffix.