docker: add Traefik support

USE_FOREIGN_CERT_MANAGER existed in compose/example.env but was never
read by any code. This wires it up end-to-end based on PR 662.

- Preliminarily add config options for this, and skip AcmetoolDeployer if
set.
- Add Traefik integration in docker/docker-compose-traefik.yaml, with
  traefik-certs-dumper
- post-hook.sh creates fullchain/privkey symlinks for chatmail
- Chatmail container uses ports 25/143/465/587/993 directly, Traefik
  handles 80/443
- docker/traefik/ contains config.yaml and dynamic configs
- docker/example-traefik.env for the Traefik setup
- rename USE_FOREIGN_CERT_MANAGER to CHATMAIL_NOACME

cmdeploy/src/cmdeploy/deployers.py

@@ -610,7 +610,12 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
         UnboundDeployer(config),
         TurnDeployer(mail_domain),
         IrohDeployer(config.enable_iroh_relay),
-        AcmetoolDeployer(config.acme_email, tls_domains),
+    ]
+
+    if not config.noacme:
+        all_deployers.append(AcmetoolDeployer(config.acme_email, tls_domains))
+
+    all_deployers += [
         WebsiteDeployer(config),
         ChatmailVenvDeployer(config),
         MtastsDeployer(),