Bundle a tested Traefik in releases, the image and the installer

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

.env.example

@@ -13,6 +13,8 @@ BLACKTIP_TOKEN=
 # Serve http/https with Traefik (path to a Traefik v3 binary), and optionally
 # use DNS challenge for wildcard certificates. The provider's credentials go here
 # too, named exactly as Traefik documents for that provider.
-#BLACKTIP_TRAEFIK=/usr/local/bin/traefik
+# Releases bundle a tested Traefik: /usr/local/lib/blacktip/traefik (systemd install),
+# /traefik (Docker image, already set; set it empty to use the built-in proxy).
+#BLACKTIP_TRAEFIK=/usr/local/lib/blacktip/traefik
 #BLACKTIP_ACME_DNS=cloudflare
 #CF_DNS_API_TOKEN=