Add web01 public reverse proxy with DNS-01 wildcard TLS

web01 terminates TLS for grafana.cnx.network and proxies to Grafana on
control over the mesh. Caddy serves a *.cnx.network wildcard cert obtained
via ACME DNS-01, using a dedicated acme_web01 TSIG key scoped on ns1 to
_acme-challenge on the cnx.network zone only. Ports 80/443 are the only
public exposure (80 just redirects); admin and the backend ride ZeroTier.

Also reload Caddy on cert renewal for both web01 and mx1, since both
reference the cert via explicit tls file paths and would otherwise keep
serving a stale cert after a silent renewal.

modules/mail.nix

@@ -117,6 +117,10 @@ in
       # Keep the private key fixed across renewals so the DANE TLSA "3 1 1"
       # record (public-key digest, published in the zone) stays valid.
       extraLegoRenewFlags = [ "--reuse-key" ];
+      # Caddy serves the MTA-STS endpoint from explicit cert file paths, so it
+      # won't notice a renewal on its own — reload it whenever the cert changes.
+      # (Merges with the postfix/dovecot reloads SNM wires up for this cert.)
+      reloadServices = [ "caddy.service" ];
     };
   };