Read SWWAF_IPV6_GROUP_PREFIX, SWWAF_MAX_TRACKED_CLIENTS and SWWAF_LOG_LEVEL (closes #112)

The IPv6 group that is one client, the size of the table of clients and
the level of the process's own lines become settings. clientGroup reads
the group length from them, so limits, bans, history, lookups, AbuseIPDB
scores and per-client anomaly counters all follow it; ratelimit.New
takes the table size; the process logger takes the level once the
settings are read, and request lines, written apart from it, are never
held back.

Judgement call: SWWAF_IPV6_GROUP_PREFIX accepts 32 to 128, the issue's example range.

Model: opus-5-5

internal/anomaly/anomaly.go

@@ -27,7 +27,8 @@ const maxCounters = 20000
 // The scopes, what a counter counts, as the settings, alerts.json and the
 // alerts name them.
 const (
-	// ScopeClient is one client: an IPv4 address, or an IPv6 /64.
+	// ScopeClient is one client: an IPv4 address, or an IPv6 netblock of
+	// SWWAF_IPV6_GROUP_PREFIX.
 	ScopeClient = "client"
 	// ScopeNet is the netblock around a client, SWWAF_ANOMALY_NET_V4_PREFIX
 	// or SWWAF_ANOMALY_NET_V6_PREFIX long.
@@ -103,7 +104,8 @@ type Counter struct {
 // Request is a request that has ended, as the counters count it.
 type Request struct {
 	// Client is the client's address, and ClientGroup the client it is
-	// counted as: its IPv4 address, or its IPv6 /64.
+	// counted as: its IPv4 address, or the IPv6 netblock of
+	// SWWAF_IPV6_GROUP_PREFIX its address is in.
 	Client      netip.Addr
 	ClientGroup netip.Prefix
 	// ASN, ASName and Country are the client's as looked up, each "" when