Give Hammerhead its own edge with a built-in dashboard route; setup.sh installs it with Blacktip instead of Caddy

HAMMERHEAD_SELF_DOMAIN creates an edge for this machine, writes its token to <data>/self-edge.env
and adds an https route for the dashboard to that edge's config, so no reverse proxy is needed.

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

cmd/hammerhead/main.go

@@ -6,6 +6,7 @@ import (
 	"flag"
 	"fmt"
 	"log"
+	"net"
 	"net/http"
 	"os"
 	"strconv"
@@ -20,6 +21,19 @@ import (
 // version is set at build time (deploy/build.sh).
 var version = "dev"
 
+// localAddr turns a listen address into one this machine can dial: ":8080" and "0.0.0.0:8080"
+// become "127.0.0.1:8080".
+func localAddr(listen string) string {
+	host, port, err := net.SplitHostPort(listen)
+	if err != nil {
+		return listen
+	}
+	if host == "" || host == "0.0.0.0" || host == "::" {
+		host = "127.0.0.1"
+	}
+	return net.JoinHostPort(host, port)
+}
+
 func env(k, def string) string {
 	if v := os.Getenv(k); v != "" {
 		return v
@@ -61,6 +75,9 @@ func main() {
 		MasterKey:        os.Getenv("HAMMERHEAD_MASTER_KEY"),
 		MetricsToken:     os.Getenv("HAMMERHEAD_METRICS_TOKEN"),
 		LogRetentionDays: days,
+		SelfDomain:       os.Getenv("HAMMERHEAD_SELF_DOMAIN"),
+		SelfTarget:       localAddr(*listen),
+		SelfTunnel:       os.Getenv("HAMMERHEAD_SELF_TUNNEL"),
 	})
 	if err != nil {
 		log.Fatal(err)