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/_io/boot.nix

@@ -0,0 +1,14 @@
+{
+  boot = {
+    # TODO check if future kernel versions fix boot issue with systemd initrd with tpm
+    initrd.systemd.tpm2.enable = false;
+    kernelParams = [
+      "nosgx"
+      "i915.fastboot=1"
+      "mem_sleep_default=deep"
+    ];
+    extraModprobeConfig = ''
+      options snd-intel-dspcfg dsp_driver=3
+    '';
+  };
+}