chore: make bootloader enabled by default

hosts/dullscythe/default.nix

···
   ];
 
   settings = {
-    bootloader = {
+    bootloader.grub = {
       enable = true;
-      
-      grub = {
-        enable = true;
-        device = "/dev/vda";
-      };
+      device = "/dev/vda";
     };
 
     profiles.server.enable = true;

hosts/solstice/default.nix

···
 {
+  settings = {
+    bootloader.enable = false;
+  };
+
   system.stateVersion = "23.11"; # Initial NixOS version
   nixpkgs.hostPlatform = "x86_64-linux";
 }

modules/nixos/boot/loader.nix

···
 { lib, ... }:
 
 {
-  options.settings.bootloader.enable = lib.mkEnableOption "Enable bootloader configuration";
+  options.settings.bootloader.enable = lib.mkOption {
+    type = lib.types.bool;
+    default = true;
+    description = "Enable the system bootloader.";
+  };
 }