Clarify bare-metal handling of generated mail service config files

[Copilot]

The bare-metal install guide skipped what happens to generated Postfix, Dovecot, and OpenDKIM config after mailserver genconfig. This update adds the missing step and aligns the README with the actual runtime behavior used by both bare-metal and Docker flows.

• Installation docs

  • Insert a new bare-metal step between initial setup and service installation covering generated config handling.
  • Clarify that mailserver genconfig writes the live config directly to system paths under /etc/postfix, /etc/dovecot, and /etc/opendkim.
  • Call out that Postfix maps are compiled during generation and DKIM private keys are written under /data/dkim.

• Operator guidance

  • Add a compact list of the generated files operators are expected to review.
  • Include quick inspection commands for validating the generated config before enabling services.
  • Note that these files are generated output and will be regenerated in place on future genconfig runs / service startup.

• Doc consistency

  • Renumber the subsequent bare-metal steps to preserve the installation flow.

mailserver genconfig

# Generated in place:
# /etc/postfix/main.cf
# /etc/dovecot/dovecot.conf
# /etc/opendkim/opendkim.conf

Original prompt

i believe there should be an step between 6 and 7 bare metal describing what to do with configuration files. check the source code to generate most accurate response. you can get help from docker stuff as well.