servewaf answers rproxy's question about each request and takes its report (closes #170)

`smallwebwaf servewaf` runs today's checks on the visitor's request each
question carries, answers rproxy, and passes nothing to an app. rproxy reports
every request servewaf answered. A report counts an allowed request's bytes and
writes servewaf's second log line. The table holds a copy of what a report
needs, never the request, so a report cannot reach a request being handled.

Judgement call: a question's body is read before any check; over 64 KiB gets 400.
Judgement call: a report's bytes and durations have ceilings, so they cannot overflow.
Judgement call: a `close` disposition for SWWAF_BAN_RESPONSE=close.

Model: opus-5-5

internal/alerts/alerts_test.go

@@ -1284,9 +1284,11 @@ func anAlertForEachEvent() []eventMessage {
 				Event: alerts.EventWAFBlock, Client: netip.MustParseAddr("192.0.2.1"),
 				Netblock: netip.MustParsePrefix("192.0.2.1/32"),
 				Reason:   "refused by the Core Rule Set",
+				Host:     "app.example",
 			},
 			"fsn1app1/gitea: waf_block", "default shield",
-			"refused by the Core Rule Set\nclient: 192.0.2.1\nnetblock: 192.0.2.1/32",
+			"refused by the Core Rule Set\nhost: app.example\nclient: 192.0.2.1\n" +
+				"netblock: 192.0.2.1/32",
 		},
 		{
 			alerts.Alert{