feat(uConsole): add disko, backlight fix, GPIO 23, mt7921u

- Add disko flake input + partition config (/boot/firmware, /, /home)
- Add cm5-backlight-fix service as display fallback
- Add enable-gpio23-usb-hub service for internal USB hub
- Add mt7921u kernel module for MediaTek AC1200 WiFi
- Add gpiod package for GPIO userspace control

hosts/uConsole/hardware-configuration.nix

@@ -9,15 +9,26 @@
   boot.initrd.kernelModules = [ ];
   boot.extraModulePackages = [ ];
 
-  # uConsole CM5 uses NVMe or eMMC for boot storage
-  # The uconsole-cm5 module sets up /boot/firmware and default /
-  # Override device label here if using different storage
-  fileSystems."/" = lib.mkDefault {
+  # uConsole CM5 eMMC partitions managed by disko
+  # Labels defined in disko-config.nix
+  fileSystems."/" = {
     device = "/dev/disk/by-label/NIXOS_UCM5";
     fsType = "ext4";
     options = [ "noatime" ];
   };
 
+  fileSystems."/boot/firmware" = {
+    device = "/dev/disk/by-label/FIRMWARE";
+    fsType = "vfat";
+    options = lib.mkForce [ "fmask=0022" "dmask=0022" ];
+  };
+
+  fileSystems."/home" = {
+    device = "/dev/disk/by-label/NIXOS_HOME";
+    fsType = "ext4";
+    options = [ "noatime" ];
+  };
+
   swapDevices = [ ];
 
   nixpkgs.hostPlatform = lib.mkDefault "aarch64-linux";