fix(mailpit): bind UI to port 8025 so healthcheck passes; revert email FROM changes

Port 0 disabled the web UI but broke the built-in /readyz healthcheck.
Binding to 8025 keeps the UI accessible within the Docker network only
(no Traefik labels) and lets the container report healthy.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mailpit/compose.yml

@@ -14,7 +14,7 @@ services:
       MP_SMTP_RELAY_PASSWORD: ${SMTP_RELAY_PASSWORD}
       MP_SMTP_RELAY_AUTH: plain
       MP_SMTP_RELAY_TLS: "true"
-      MP_UI_BIND_ADDR: 0.0.0.0:0
+      MP_UI_BIND_ADDR: 0.0.0.0:8025
     volumes:
       - ../.data/mailpit:/data
     restart: always