feat(uconsole): add cm5 cross-compiled nixosConfiguration

- New host: uconsole-cm5 (aarch64-linux, cross-built from x86_64)
- SSH authorizedKeys: gortium.main + ai-worker.main
- NetworkManager enabled (WiFi password via agenix later)
- Display: vc4/panel_cwu50/rp1_dsi with empty initrd
- Config.txt [pi5] section (not [cm5])
- Backlight fix service
- nixos-raspberrypi → gortium/cm5-cross-v1 fork (PR #197)
- nixpkgs-uconsole pinned to nixos-25.11 (kernel patch compat)

V3 branch saved as archive/uconsole-cm5-v3 (Reticulum/SDR/HAM config).

hosts/uconsole-cm5/hardware-configuration.nix

@@ -0,0 +1,30 @@
+{ config, lib, pkgs, modulesPath, ... }:
+
+{
+  imports = [
+    (modulesPath + "/installer/scan/not-detected.nix")
+  ];
+
+  boot.initrd.availableKernelModules = [ "xhci_pci" "usbhid" "usb_storage" "sdhci_pci" "nvme" ];
+  boot.initrd.kernelModules = [ ];
+  boot.extraModulePackages = [ ];
+
+  # SD card partitions (nixos-uconsole layout)
+  fileSystems."/" = {
+    device = "/dev/disk/by-label/NIXOS_SD";
+    fsType = "ext4";
+    options = [ "noatime" ];
+  };
+
+  fileSystems."/boot/firmware" = {
+    device = "/dev/disk/by-label/FIRMWARE";
+    fsType = "vfat";
+    options = [ "fmask=0022" "dmask=0022" ];
+  };
+
+  swapDevices = [ ];
+
+  nixpkgs.hostPlatform = lib.mkDefault "aarch64-linux";
+  hardware.enableRedistributableFirmware = true;
+  powerManagement.cpuFreqGovernor = lib.mkDefault "ondemand";
+}