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>

dev/compose.yaml

@@ -32,11 +32,9 @@ services:
       GITEA__server__SSH_PORT: 2222
       GITEA__server__SSH_LISTEN_PORT: 2222
       GITEA__mailer__ENABLED: true
-      GITEA__mailer__PROTOCOL: smtps
-      GITEA__mailer__SMTP_ADDR: ${EMAIL_SMTP_HOST}
-      GITEA__mailer__SMTP_PORT: ${EMAIL_SMTP_PORT}
-      GITEA__mailer__USER: ${EMAIL_SMTP_USER}
-      GITEA__mailer__PASSWD: ${EMAIL_SMTP_PASSWORD}
+      GITEA__mailer__PROTOCOL: smtp
+      GITEA__mailer__SMTP_ADDR: net_mailpit
+      GITEA__mailer__SMTP_PORT: 1025
       GITEA__mailer__FROM: ${EMAIL_FROM}
       GITEA__service__DISABLE_REGISTRATION: false
       GITEA__service__REQUIRE_SIGNIN_VIEW: false
@@ -200,12 +198,10 @@ services:
       N8N_PROTOCOL: https
       WEBHOOK_URL: https://${DEV_N8N_TRAEFIK_HOST}/
       N8N_EMAIL_MODE: smtp
-      N8N_SMTP_HOST: ${EMAIL_SMTP_HOST}
-      N8N_SMTP_PORT: ${EMAIL_SMTP_PORT}
-      N8N_SMTP_USER: ${EMAIL_SMTP_USER}
-      N8N_SMTP_PASS: ${EMAIL_SMTP_PASSWORD}
+      N8N_SMTP_HOST: net_mailpit
+      N8N_SMTP_PORT: 1025
       N8N_SMTP_SENDER: ${EMAIL_FROM}
-      N8N_SMTP_SSL: "true"
+      N8N_SMTP_SSL: "false"
       MATTERMOST_WEBHOOK_URL: ${MATTERMOST_WEBHOOK_URL:-}
     depends_on:
       - postgres
@@ -243,9 +239,8 @@ services:
       URL_HOST: ${DEV_ASCIINEMA_TRAEFIK_HOST}
       URL_SCHEME: https
       DATABASE_URL: postgresql://${DB_USER}:${DB_PASSWORD}@${CORE_DB_HOST}/${DEV_ASCIINEMA_DB_NAME}?pool_size=10
-      SMTP_HOST: ${EMAIL_SMTP_HOST}
-      SMTP_USERNAME: ${EMAIL_SMTP_USER}
-      SMTP_PASSWORD: ${EMAIL_SMTP_PASSWORD}
+      SMTP_HOST: net_mailpit
+      SMTP_PORT: 1025
       SMTP_FROM_ADDRESS: ${EMAIL_FROM}
       SIGN_UP_DISABLED: ${DEV_ASCIINEMA_SIGN_UP_DISABLED:-false}
       DEFAULT_AVATAR: gravatar