A Grafana dashboard for iPX

Built on what the monitoring project already collects: the container's
log in Loki (through Alloy) and the traces in Tempo. It parses the
access log and the event log's wire JSON, so there are no metrics to
add to ipx: what is waiting and downloaded (from the healthcheck's
status), new items, downloads and bytes, failing feeds and downloads,
requests by status and response time, the slowest and busiest paths,
recent and slow traces, and the log. Provisioned from a file, so it is
regenerated here, not edited in Grafana.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- A Grafana dashboard for iPX, from its log in Loki and its traces in Tempo (`grafana/dashboard.py`).
 - With `OTEL_EXPORTER_OTLP_ENDPOINT` set, the daemon sends traces of its scans, downloads and web
   requests to a collector such as Tempo.
 - A feed that has no artwork of its own shows its website's icon instead.