docs: hardware support guide + product backlog

Add docs/HARDWARE.md (layers, install path, firmware/fingerprint/NVIDIA
deep dives, unsupported machines, contributing a DMI line). Link from
README and MIGRATION; queue firmware UI, doctor checks, detect-hw CLI,
and related PROPOSED items in BACKLOG.

docs/MIGRATION.md

@@ -117,6 +117,8 @@ cp /etc/nixos/hosts/TuringMachine/hardware-configuration.nix ./hardware-configur
       # Optional nixos-hardware profile(s) for your model. For an AMD laptop:
       #   hardwareProfile = [ "common-cpu-amd-pstate" "common-gpu-amd" "common-pc-laptop-ssd" ];
       # Names: https://github.com/NixOS/nixos-hardware  (verify before use)
+      # Full hardware story (firmware, fingerprint, unsupported machines):
+      #   docs/HARDWARE.md in the Nomarchy repo
     };
 }
 ```