refactor: overhaul pretty much all the organization

deploy/rpi5/default.nix

@@ -0,0 +1,18 @@
+{ config, lib }:
+{
+  options.aether.deploy.rpi5 = {
+    kernelPackages = lib.mkOption {
+      type = lib.types.raw;
+      description = "Kernel package to use for Raspberry Pi 5 support";
+    };
+  };
+
+  config =
+    let cfg = config.aether.deploy.rpi5;
+    in {
+      nixpkgs.system = "aarch64-linux";
+      boot.kernelPackages = cfg.kernelPackages;
+      boot.loader.systemd-boot.enable = true;
+      boot.loader.efi.canTouchEfiVariables = false;
+    };
+}