[Feature] Add filesystem-consistent VM snapshots

Following CONTRIBUTING.md, I would like to confirm interest before submitting this feature.

The Snapshots feature provides fast local recovery points for the Omarchy VM. Users can create, manage, retain, and restore snapshots before risky system changes.

Each snapshot is an APFS copy-on-write clone of the entire VM rootfs.ext4. Online creation briefly freezes the guest filesystem and pauses QEMU to ensure consistency, then immediately resumes the VM.

Important behavior:

• Restore is limited to the same guest build.
• Restore rolls back the entire disk, including /home, unlike native Omarchy snapshots.
• RAM is not saved, so this is not suspend.
• Snapshots remain on the VM's APFS volume and are not backups.

The prototype already includes guest and host watchdogs, transactional restore rollback, retention, and fault tests.

Would this feature be accepted as a contribution?