Ban notes name the reputation sources that listed the client (closes #109)

A ban's notes, in bans.json and in its alert, gain `reputation`: each
blocklist, DNSBL zone or AbuseIPDB that listed the client when the ban
was made, as its `source`, named and ordered as in the request log's
`reputation`, with AbuseIPDB's `score`. It is left out when none did.
README.md shows it in a bans.json example.

Notes now hold a list, so bans can no longer be compared with ==: the
tests compare them with reflect.DeepEqual.

Judgement call: the score is a pointer, so a score of 0, a hit while
SWWAF_ABUSEIPDB_MIN_SCORE is 0, is still written.

Model: opus-5-5

internal/bans/snapshot_test.go

@@ -2,6 +2,7 @@ package bans_test
 
 import (
 	"net/netip"
+	"reflect"
 	"slices"
 	"strings"
 	"testing"
@@ -224,7 +225,7 @@ func TestLoadKeepsAtMostMaxBansDroppingTheEarliest(t *testing.T) {
 	ledger.Load([]bans.Ban{later, earlier})
 
 	held := ledger.Snapshot()
-	if len(held) != 1 || held[0] != later {
+	if len(held) != 1 || !reflect.DeepEqual(held[0], later) {
 		t.Errorf("the ledger holds %+v, want only the ban that began later", held)
 	}
 }
@@ -267,7 +268,7 @@ func TestLoadReplacesTheBansHeld(t *testing.T) {
 		bans.Notes{})
 
 	want := []bans.Ban{first, second, kept}
-	if got := ledger.Snapshot(); !slices.Equal(got, want) {
+	if got := ledger.Snapshot(); !reflect.DeepEqual(got, want) {
 		t.Errorf("the ledger holds %+v, want %+v", got, want)
 	}
 }