Guard: watch logs, ban misbehaving addresses in Housecarl

Files and the journal, patterns with one <IP>, bounties within a window,
bans in a Housecarl ban list with repeat offenders' bans growing; presets
for sshd, jarl, housecarl, steward, bind-xfr, postfix-sasl, dovecot,
nginx-auth and housecarl-drops; guard run/check/test/status/bans/ban/unban;
a Debian package with a sandboxed unit; an end-to-end test with Housecarl.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/match/match_test.go

@@ -0,0 +1,50 @@
+package match
+
+import (
+	"net/netip"
+	"testing"
+)
+
+func TestMatch(t *testing.T) {
+	m, err := Compile([]string{`from <IP> port`, `client: <IP>,`, `^conn <IP>$`}, []string{`trusted-scanner`})
+	if err != nil {
+		t.Fatal(err)
+	}
+	cases := map[string]string{
+		"from 203.0.113.9 port 22":                 "203.0.113.9",
+		"from 2001:db8::9 port 22":                 "2001:db8::9",
+		"from ::ffff:203.0.113.9 port 22":          "203.0.113.9",
+		"from [2001:db8::9] port 22":               "2001:db8::9",
+		"from fe80::1%eth0 port 22":                "fe80::1",
+		"client: 203.0.113.9, server":              "203.0.113.9",
+		"conn 2001:db8:1:2:3:4:5:6":                "2001:db8:1:2:3:4:5:6",
+		"from 12:34:56 port 22":                    "", // a time, not an address
+		"from 999.1.1.1 port 22":                   "",
+		"from 203.0.113.9 port 22 trusted-scanner": "", // ignored
+		"nothing here":                             "",
+	}
+	for line, want := range cases {
+		a, ok := m.Match(line)
+		if got := map[bool]string{true: a.String(), false: ""}[ok]; got != want {
+			t.Errorf("%q: %q, want %q", line, got, want)
+		}
+	}
+	if _, err := Compile([]string{"<IP> and <IP>"}, nil); err == nil {
+		t.Error("two <IP> accepted")
+	}
+	if _, err := Compile([]string{"<IP> (unclosed"}, nil); err == nil {
+		t.Error("a broken pattern accepted")
+	}
+}
+
+func TestGroup(t *testing.T) {
+	if g := Group(netip.MustParseAddr("2001:db8:1:2:aa::1"), 64); g.String() != "2001:db8:1:2::/64" {
+		t.Errorf("/64: %s", g)
+	}
+	if g := Group(netip.MustParseAddr("203.0.113.9"), 64); g.String() != "203.0.113.9/32" {
+		t.Errorf("IPv4: %s", g)
+	}
+	if g := Group(netip.MustParseAddr("2001:db8::1"), 128); g.String() != "2001:db8::1/128" {
+		t.Errorf("/128: %s", g)
+	}
+}