fix: IPMI access for bee user + remove chart legend

- Add udev rule: /dev/ipmi0 readable by 'ipmi' group (no sudo needed)
- Add 'ipmi' group creation and bee user membership in chroot hook
- Remove legend from all charts (data shown in GPU table below)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/webui/server.go

@@ -625,7 +625,7 @@ func renderChartSVG(title string, datasets [][]float64, names []string, labels [
 	opt := gocharts.NewLineChartOptionWithData(datasets)
 	opt.Title = gocharts.TitleOption{Text: title}
 	opt.XAxis.Labels = sparse
-	opt.Legend = gocharts.LegendOption{SeriesNames: names}
+	opt.Legend = gocharts.LegendOption{SeriesNames: names, Show: gocharts.Ptr(false)}
 	if yMin != nil || yMax != nil {
 		opt.YAxis = []gocharts.YAxisOption{{
 			Min:            yMin,