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>

.env.example

@@ -21,6 +21,14 @@ HAMMERHEAD_MASTER_KEY=
 # Leave empty and /metrics does not exist.
 #HAMMERHEAD_METRICS_TOKEN=
 
+# Serve the dashboard through a Blacktip edge on this same machine, at this name, with an
+# automatic HTTPS certificate: no Caddy or other web server in front of Hammerhead. Hammerhead
+# makes the edge itself and writes its token to <data>/self-edge.env (BLACKTIP_TOKEN=...).
+# deploy/setup.sh --domain sets this up for you. Needs HAMMERHEAD_URL set to the same name.
+#HAMMERHEAD_SELF_DOMAIN=hammerhead.example.com
+# The edge's public WireGuard address for sites; default <HAMMERHEAD_SELF_DOMAIN>:51820.
+#HAMMERHEAD_SELF_TUNNEL=hammerhead.example.com:51820
+
 # How long access logs are kept (days). Default 30.
 #HAMMERHEAD_LOG_DAYS=30