fix: Postfix dev relay vers Mailpit pour capturer tous les emails

- RELAYHOST changé de "" vers "[mailpit]:1025" : tous les emails
  sortants passent par Mailpit (visible sur http://localhost:8025)
- smtp_tls_security_level=none : pas de TLS vers Mailpit en dev
- depends_on mailpit ajouté pour garantir le démarrage

En prod : RELAYHOST sera vide (envoi direct) ou vers AWS SES.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose-dev.yml

@@ -192,7 +192,7 @@ services:
     hostname: mail.siteconseil.local
     environment:
       ALLOWED_SENDER_DOMAINS: siteconseil.fr siteconseil.local
-      RELAYHOST: ""
+      RELAYHOST: "[mailpit]:1025"
       POSTFIX_myhostname: mail.siteconseil.local
       POSTFIX_mydestination: siteconseil.local, localhost
       POSTFIX_mynetworks: "10.0.0.0/8 172.16.0.0/12 192.168.0.0/16"
@@ -200,11 +200,14 @@ services:
       POSTFIX_non_smtpd_milters: "inet:rspamd:11332"
       POSTFIX_milter_protocol: "6"
       POSTFIX_milter_default_action: "accept"
+      POSTFIX_smtp_tls_security_level: "none"
     volumes:
       - postfix-data:/var/spool/postfix
     depends_on:
       rspamd:
         condition: service_started
+      mailpit:
+        condition: service_started
     healthcheck:
       test: ["CMD-SHELL", "postfix status || exit 1"]
       interval: 10s