Test la connexion SMTP avant persistance (BUG-INT-10 T2.4).

Test la connexion SMTP avant persistance (BUG-INT-10 T2.4).

Body :
    {
      "host": "smtp.brevo.com",
      "port": 587,
      "username": "user@domain.tld",
      "password": "<api_key_or_password>",
      "from_email": "no-reply@indusforge.fr",
      "from_name": "eyeot Software",
      "encryption": "starttls" | "ssl" | "none",
      "to": "admin@org.tld"
    }

Retour 200 : `{success: true, message: str, latency_ms: int}`
Retour 422 : RFC 7807 si validation OU envoi failed (timeout/auth/connection).

NE persiste PAS d'Integration — test pur. Permission `admin:settings`.

Permissions requises : admin:settings