feat: grub and greetd setups

grub: changed theme to distro-grub-themes

kernel: upgraded to linux zen kernel

greetd: configured tuigreet with greetd to replace sddm

nixos/greetd.nix

@@ -0,0 +1,33 @@
+{
+  pkgs,
+  config,
+  lib,
+  ...
+}: let
+  tuigreet = "${pkgs.greetd.tuigreet}/bin/tuigreet";
+in {
+  services.greetd = {
+    enable = true;
+    settings = {
+      default_session = {
+        command = "${tuigreet} --time --remember --cmd Hyprland";
+        user = "greeter";
+      };
+    };
+  };
+
+  # this is a life saver.
+  # literally no documentation about this anywhere.
+  # might be good to write about this...
+  # https://www.reddit.com/r/NixOS/comments/u0cdpi/tuigreet_with_xmonad_how/
+  systemd.services.greetd.serviceConfig = {
+    Type = "idle";
+    StandardInput = "tty";
+    StandardOutput = "tty";
+    StandardError = "journal"; # Without this errors will spam on screen
+    # Without these bootlogs will spam on screen
+    TTYReset = true;
+    TTYVHangup = true;
+    TTYVTDisallocate = true;
+  };
+}