Add LAN-only status UI for caddy-autogen

Apps/caddy-autogen/caddy/Caddyfile

@@ -2,6 +2,19 @@
   admin {$CADDY_ADMIN}
 }
 
+:31820 {
+  @allowed remote_ip private_ranges
+  handle @allowed {
+    @status_json path /status.json
+    handle @status_json {
+      reverse_proxy discovery-agent:8089
+    }
+    root * /srv/status
+    file_server
+  }
+  respond "forbidden" 403
+}
+
 :80 {
   respond "caddy-autogen initializing" 200
 }