feat(hecuba): switch to UEFI (and modularize)

modules/bootloader/default.nix

@@ -1,17 +1,31 @@
 { lib, config, ... }:
 
 {
-  options.bootloader.enable = lib.mkOption {
-    default = false;
-    type = lib.types.bool;
-  };
-
-  config = lib.mkIf config.bootloader.enable {
-    boot = {
-      loader = {
-        systemd-boot.enable = true;
-        efi.canTouchEfiVariables = true;
-      };
+  options.bootloader = {
+    enable = lib.mkOption {
+      default = false;
+      type = lib.types.bool;
+    };
+    firmware = lib.mkOption {
+      default = "uefi";
+      type = lib.types.enum [
+        "bios"
+        "uefi"
+      ];
     };
   };
+
+  config = lib.mkIf config.bootloader.enable (
+    lib.mkMerge [
+      (lib.mkIf (config.bootloader.firmware == "uefi") {
+        boot.loader = {
+          systemd-boot.enable = true;
+          efi.canTouchEfiVariables = true;
+        };
+      })
+      (lib.mkIf (config.bootloader.firmware == "bios") {
+        boot.loader.grub.enable = true;
+      })
+    ]
+  );
 }