add aspects/hosts/ configurations

Host-specific NixOS configurations for:
- alexandria (server)
- io (desktop)
- rotterdam (desktop)
- trantor (server, aarch64)

Each host has a main config file and _hostname/ directory
with hardware-configuration and other host-specific modules.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

aspects/hosts/_rotterdam/hardware-configuration.nix

@@ -0,0 +1,82 @@
+{
+  config,
+  lib,
+  modulesPath,
+  ...
+}:
+
+{
+  imports = [ (modulesPath + "/installer/scan/not-detected.nix") ];
+
+  boot = {
+    initrd = {
+      availableKernelModules = [
+        "amdgpu"
+        "nvme"
+        "xhci_pci"
+        "ahci"
+        "usbhid"
+        "sd_mod"
+      ];
+      luks.devices."cryptroot" = {
+        device = "/dev/disk/by-uuid/f7dd4142-7109-4493-834d-4a831777f08d";
+        keyFile = "/dev/disk/by-partuuid/add5fc14-e20f-48be-8b2a-0799ef04d3cb";
+      };
+    };
+    kernelModules = [ "kvm-amd" ];
+  };
+
+  fileSystems = {
+    "/" = {
+      device = "/dev/disk/by-uuid/3287dbc3-c0fa-4096-a0b3-59b017cfecc8";
+      fsType = "btrfs";
+      options = [
+        "subvol=@root"
+        "noatime"
+        "compress=zstd"
+      ];
+    };
+    "/home" = {
+      device = "/dev/disk/by-uuid/3287dbc3-c0fa-4096-a0b3-59b017cfecc8";
+      fsType = "btrfs";
+      options = [
+        "subvol=@home"
+        "noatime"
+        "compress=zstd"
+      ];
+    };
+    "/boot/efi" = {
+      device = "/dev/disk/by-uuid/F2A2-CF5A";
+      fsType = "vfat";
+      options = [
+        "noatime"
+        "fmask=0077"
+        "dmask=0077"
+      ];
+    };
+    "/nix" = {
+      device = "/dev/disk/by-uuid/3287dbc3-c0fa-4096-a0b3-59b017cfecc8";
+      fsType = "btrfs";
+      options = [
+        "subvol=@nix"
+        "noatime"
+        "compress=zstd"
+      ];
+    };
+    "/persistent" = {
+      device = "/dev/disk/by-uuid/3287dbc3-c0fa-4096-a0b3-59b017cfecc8";
+      fsType = "btrfs";
+      options = [
+        "subvol=@persistent"
+        "noatime"
+        "compress=zstd"
+      ];
+    };
+  };
+
+  networking.useDHCP = lib.mkDefault true;
+
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
+
+  hardware.cpu.amd.updateMicrocode = lib.mkDefault config.hardware.enableRedistributableFirmware;
+}