Sets from Jarl: sets holding the addresses of names in Jarl

A set can take its addresses from Jarl: every A and AAAA record of its
names (NAME@VIEW), CNAMEs followed within Jarl's zones in the same view.
housecarld reads them every jarl.refresh and after each change, keeps
only the addresses within the zones and networks the set allows, and
keeps what it last read (saved in the database and the boot ruleset)
while Jarl can't be reached. A change of the addresses applies the
ruleset again without a history entry and is audited (set.jarl).

hc set add --jarl --within, hc set jarl; the kind "from Jarl" and
Addresses… on the Sets page; GET /sets/{name}/jarl and /jarl/refresh;
validation codes set_jarl_*, status warnings jarl_*; docs/jarl.md.
e2e phase with scripts/fakejarl.

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

internal/config/config.go

@@ -153,6 +153,8 @@ type Jarl struct {
 	// CACert is a PEM file with a CA to trust for Jarl's certificate.
 	CACert   string `yaml:"ca_cert"`
 	Insecure bool   `yaml:"insecure"`
+	// Refresh is how often the Jarl sets' names are read (docs/jarl.md).
+	Refresh Duration `yaml:"refresh"`
 }
 
 // Enabled reports whether a Jarl server is configured.
@@ -238,6 +240,7 @@ func Default() *Config {
 			Retention: StatsRetention{Minute: Duration(7 * 24 * time.Hour), Hour: Duration(90 * 24 * time.Hour), Day: Duration(730 * 24 * time.Hour)}},
 		Shadow: Shadow{Position: ShadowAfter},
 		Names:  Names{Enabled: true, Cache: Duration(10 * time.Minute)},
+		Jarl:   Jarl{Refresh: Duration(time.Minute)},
 		TLS:    TLS{ACME: ACME{Directory: "letsencrypt-staging", Resolvers: []string{"1.1.1.1:53", "9.9.9.9:53", "8.8.8.8:53"}, CheckPropagation: true}},
 	}
 }
@@ -320,6 +323,9 @@ func (c *Config) check() error {
 	if c.Names.Cache <= 0 {
 		return fmt.Errorf("names.cache must be a duration, such as 10m")
 	}
+	if c.Jarl.Refresh < Duration(10*time.Second) {
+		return fmt.Errorf("jarl.refresh must be a duration of 10s or more, such as 1m")
+	}
 	return nil
 }