New `arca create <device> <alias>` command that formats a device with
LUKS encryption, creates a filesystem, optionally enrolls a FIDO2
keyslot, and adds the device to the arca config.
Adds Makefile with arca, vet, lint, test, and clean targets.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
