Introduces a single, idempotent baseline role to supersede the
overlapping day0-baseline and common roles. Capabilities are
feature-flagged so they can be toggled per-host:
- packages (common + OS-family + per-host extras)
- timezone + locale
- chrony time sync against sundial
- baseline users (jarvis admin account with SSH key + NOPASSWD sudo)
- SSH hardening via /etc/ssh/sshd_config.d/ drop-in
- unattended security upgrades (Debian family)
- sysctl drop-in at /etc/sysctl.d/99-mk-labs.conf
- journald retention caps
- branded MOTD
Ubuntu/Debian is first-class; vars/RedHat.yml provides a placeholder
for future distros via the ansible_os_family pattern.
The legacy day0-baseline and common roles remain in place for now and
will be removed during the playbook cleanup sweep, alongside the
existing playbook naming inconsistencies.
