chore: refactor system modules

system/boot/plymouth.nix

@@ -0,0 +1,33 @@
+{
+  pkgs,
+  lib,
+  config,
+  ...
+}:
+with lib; let
+  cfg = config.system.boot.plymouth;
+in {
+  options.system.boot.plymouth.enable = mkEnableOption "Enables Plymouth at system boot";
+  config.boot = mkIf cfg.enable {
+    plymouth = {
+      inherit (cfg) enable;
+      theme = "circle_hud";
+      themePackages = with pkgs; [
+        (adi1090x-plymouth-themes.override {
+          selected_themes = ["circle_hud"];
+        })
+      ];
+    };
+    consoleLogLevel = 3;
+    initrd.verbose = false;
+    kernelParams = [
+      "quiet"
+      "splash"
+      "boot.shell_on_fail"
+      "udev.log_priority=3"
+      "rd.systemd.show_status=auto"
+    ];
+    # Loader appears only if a key is pressed
+    loader.timeout = 0;
+  };
+}