chore: refactor system modules

system/default.nix

@@ -0,0 +1,40 @@
+{
+  lib,
+  config,
+  ...
+}:
+with lib; let
+  cfg = config.system.misc;
+in {
+  imports = [
+    ./boot
+    ./desktop
+    ./dev
+    ./hardware
+    ./i18n
+    ./network
+    ./packages
+    ./security
+    ./services
+    ./users
+  ];
+
+  options.system.misc = {
+    timezone = mkOption {
+      type = types.str;
+      default = "Europe/Paris";
+    };
+    keymap = mkOption {
+      type = types.str;
+      default = "fr";
+      example = "fr-bepo";
+      description = "Keymap to use in the TTY console";
+    };
+  };
+
+  config = {
+    boot.tmp.cleanOnBoot = true;
+    time.timeZone = cfg.timezone;
+    console.keyMap = cfg.keymap;
+  };
+}