feat: add Mailpit SMTP relay and migrate all services

- Add Mailpit service to NET stack with web UI at mailpit.pivoine.art
- Configure Mailpit to relay all emails through IONOS SMTP
- Migrate all 11+ services to use Mailpit instead of direct IONOS SMTP:
  * SEXY: Directus API
  * UTIL: Joplin, Mattermost, Vaultwarden, Tandoor, Linkwarden
  * DEV: Gitea, n8n, Asciinema
  * AI: Open WebUI
  * NET: Netdata (via msmtp)
- Centralize SMTP credentials in mailpit-relay.yaml
- Simplify service configs (no auth/TLS for internal SMTP)
- Enable email monitoring via Mailpit web UI with Basic Auth

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

util/compose.yaml

@@ -54,11 +54,9 @@ services:
       POSTGRES_USER: ${DB_USER}
       POSTGRES_PASSWORD: ${DB_PASSWORD}
       MAILER_ENABLED: 1
-      MAILER_HOST: ${EMAIL_SMTP_HOST}
-      MAILER_PORT: ${EMAIL_SMTP_PORT}
-      MAILER_SECURE: 1
-      MAILER_AUTH_USER: ${EMAIL_SMTP_USER}
-      MAILER_AUTH_PASSWORD: ${EMAIL_SMTP_PASSWORD}
+      MAILER_HOST: net_mailpit
+      MAILER_PORT: 1025
+      MAILER_SECURE: 0
       MAILER_NOREPLY_NAME: Joplin Server
       MAILER_NOREPLY_EMAIL: ${EMAIL_FROM}
     networks:
@@ -97,7 +95,7 @@ services:
       BASE_URL: https://${UTIL_LINKS_TRAEFIK_HOST}
       NEXT_PUBLIC_EMAIL_PROVIDER: true
       EMAIL_FROM: ${EMAIL_FROM}
-      EMAIL_SERVER: ${LINKS_EMAIL_SERVER}
+      EMAIL_SERVER: smtp://net_mailpit:1025
     volumes:
       - linkwarden_data:/data/data
     depends_on:
@@ -156,12 +154,10 @@ services:
       MM_SERVICESETTINGS_SITEURL: https://${UTIL_MATTERMOST_TRAEFIK_HOST}
       MM_SERVICESETTINGS_ENABLELOCALMODE: "true"
       # Email settings
-      MM_EMAILSETTINGS_ENABLESMTPAUTH: "true"
-      MM_EMAILSETTINGS_SMTPUSERNAME: ${EMAIL_SMTP_USER}
-      MM_EMAILSETTINGS_SMTPPASSWORD: ${EMAIL_SMTP_PASSWORD}
-      MM_EMAILSETTINGS_SMTPSERVER: ${EMAIL_SMTP_HOST}
-      MM_EMAILSETTINGS_SMTPPORT: ${EMAIL_SMTP_PORT}
-      MM_EMAILSETTINGS_CONNECTIONSECURITY: TLS
+      MM_EMAILSETTINGS_ENABLESMTPAUTH: "false"
+      MM_EMAILSETTINGS_SMTPSERVER: net_mailpit
+      MM_EMAILSETTINGS_SMTPPORT: 1025
+      MM_EMAILSETTINGS_CONNECTIONSECURITY: ""
       MM_EMAILSETTINGS_FEEDBACKNAME: Mattermost
       MM_EMAILSETTINGS_FEEDBACKEMAIL: ${EMAIL_FROM}
       MM_EMAILSETTINGS_REPLYTOADDRESS: ${EMAIL_FROM}
@@ -200,13 +196,11 @@ services:
       SIGNUPS_ALLOWED: ${UTIL_VAULT_SIGNUPS_ALLOWED:-false}
       INVITATIONS_ALLOWED: ${UTIL_VAULT_INVITATIONS_ALLOWED:-true}
       SHOW_PASSWORD_HINT: ${UTIL_VAULT_SHOW_PASSWORD_HINT:-false}
-      SMTP_HOST: ${EMAIL_SMTP_HOST}
+      SMTP_HOST: net_mailpit
       SMTP_FROM: ${EMAIL_FROM}
       SMTP_FROM_NAME: Vaultwarden
-      SMTP_SECURITY: force_tls
-      SMTP_PORT: ${EMAIL_SMTP_PORT}
-      SMTP_USERNAME: ${EMAIL_SMTP_USER}
-      SMTP_PASSWORD: ${EMAIL_SMTP_PASSWORD}
+      SMTP_SECURITY: off
+      SMTP_PORT: 1025
     networks:
       - compose_network
     labels:
@@ -248,12 +242,10 @@ services:
       REVERSE_PROXY_AUTH: ${UTIL_TANDOOR_REVERSE_PROXY_AUTH:-0}
 
       # Email configuration (IONOS SMTP)
-      EMAIL_HOST: ${EMAIL_SMTP_HOST}
-      EMAIL_PORT: ${EMAIL_SMTP_PORT}
-      EMAIL_HOST_USER: ${EMAIL_SMTP_USER}
-      EMAIL_HOST_PASSWORD: ${EMAIL_SMTP_PASSWORD}
-      EMAIL_USE_TLS: ${UTIL_TANDOOR_EMAIL_USE_TLS:-0}
-      EMAIL_USE_SSL: ${UTIL_TANDOOR_EMAIL_USE_SSL:-1}
+      EMAIL_HOST: net_mailpit
+      EMAIL_PORT: 1025
+      EMAIL_USE_TLS: 0
+      EMAIL_USE_SSL: 0
       DEFAULT_FROM_EMAIL: ${EMAIL_FROM}
 
       # Gunicorn settings