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/proxy/bans_test.go

@@ -7,6 +7,7 @@ import (
 	"maps"
 	"net/http"
 	"net/netip"
+	"reflect"
 	"slices"
 	"sync"
 	"testing"
@@ -312,7 +313,7 @@ func TestBanNotes(t *testing.T) {
 	ledger := server.Ledger
 
 	got := ledger.Bans(netblock)
-	if len(got) != 1 || got[0] != want {
+	if len(got) != 1 || !reflect.DeepEqual(got[0], want) {
 		t.Fatalf("bans\n%+v\nwant\n%+v", got, want)
 	}