fix(live-iso): stop initrd GPU panic + clear install pointer on login

- boot.initrd.kernelModules force-loaded amdgpu+radeon+nouveau+i915 in the
  live ISO, panicking on hosts where more than one driver matched the GPU.
  Move them to availableKernelModules so udev only loads what fits.
- Override services.getty.helpLine with a Nomarchy welcome that points at
  `sudo /etc/install.sh` (+ --dry-run / --resume variants). Replaces the
  upstream "NixOS" message.
- Ship installer/hardware-db.sh as /etc/hardware-db.sh so the installer's
  auto-detection works when invoked from the live ISO.
- Add live-ISO-only Hyprland exec-once: notify-send + an alacritty
  "Nomarchy Installer" terminal that prints the install commands. The
  graphical autologin user now sees a pointer instead of guessing how to
  start the install.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

flake.nix

@@ -144,6 +144,15 @@
             home-manager.users.nixos = {
               imports = [ ./features ];
               home.stateVersion = "25.11";
+
+              # Live-ISO-only welcome. Pops a notification a few seconds
+              # after the graphical session is up and opens a terminal
+              # parked at the installer command, so the user never has to
+              # hunt for it.
+              wayland.windowManager.hyprland.extraConfig = nixpkgs.lib.mkAfter ''
+                exec-once = sh -c 'sleep 3; notify-send -u critical -t 0 "Welcome to Nomarchy" "Run \`sudo /etc/install.sh\` in the open terminal — or \`--dry-run\` to preview."'
+                exec-once = sh -c 'sleep 4; alacritty --title "Nomarchy Installer" -e bash -lc "echo; echo \"Welcome to the Nomarchy live ISO.\"; echo; echo \"  sudo /etc/install.sh           # install\"; echo \"  sudo /etc/install.sh --dry-run # preview only\"; echo \"  sudo /etc/install.sh --resume  # resume after an interrupt\"; echo; exec bash"'
+              '';
             };
           }
         ];