Preserve console fonts when applying a keymap

[resolvicomai]

omarchy-mac-setup sets FONT=ter-132b before applying the console keymap. systemd-firstboot --keymap=… --force then rewrites vconsole.conf with keymap/XKB settings, removing the font configuration. The running console can still look correct because setfont already ran, while later boots lose the persisted font.

Preserve FONT, FONT_MAP and FONT_UNIMAP in the shared apply_keymap function, covering both initial setup and --step keymap. Keep the existing keymap conversion and reuse the existing OMARCHY_VCONSOLE_CONF override for isolated regression testing.

Validation:

• Reproduced font loss against quattro@79b074a with a firstboot stub that replaces the file; the original implementation loses all three font records.
• New shell regression passes for overwrite, repeat application without duplicates, localectl fallback, no font settings and a missing configuration file.
• Independent QA and diff review passed; command metadata passes for 469 commands and syntax checks pass for 472 commands.
• Local checks ran on macOS with Bash 5 and an external temporary adapter for GNU sed -i syntax. Full ./test/all is not green locally: /bin/bash is 3.2 and Linux tool/dependency assumptions fail. No Linux boot or physical console validation is claimed; Linux CI remains required.

AI-assisted implementation, QA and review using Codex. No changes to keyboard layout/variant selection.