Add host printer configs and refactor printing

Add printers.nix for Garand‑Desktop, Garand‑Laptop, and default hosts
with
printer definitions and a printEnable flag. Disable NFS by default in
the
host variables. Rewrite modules/core/printing.nix to import printer
settings, enable services only when printing is enabled, and add more
CUPS/Avahi options plus hardware.printers configuration. Add the lpadmin
group to the main user. Update the Messenger desktop entry URL to the
Facebook Messages page.

modules/core/printing.nix

@@ -1,18 +1,38 @@
-{host, ...}: let
-  inherit (import ../../hosts/${host}/variables.nix) printEnable;
+{
+  pkgs,
+  lib,
+  host,
+  ...
+}: let
+  inherit (import ../../hosts/${host}/printers.nix) printEnable ensureDefaultPrinter ensurePrinters;
 in {
-  services = {
+  services = lib.mkIf printEnable {
     printing = {
-      enable = printEnable;
-      drivers = [
-        # pkgs.hplipWithPlugin
+      enable = true;
+      drivers = with pkgs; [
+        cups-filters
+        cups-browsed
       ];
-    };
-    avahi = {
-      enable = printEnable;
-      nssmdns4 = true;
+      listenAddresses = ["*:631"];
+      allowFrom = ["all"];
+      browsing = true;
+      defaultShared = true;
       openFirewall = true;
     };
-    ipp-usb.enable = printEnable;
+    avahi = {
+      enable = true;
+      nssmdns4 = true;
+      openFirewall = true;
+      publish = {
+        enable = true;
+        userServices = true;
+      };
+    };
+    ipp-usb.enable = true;
+  };
+
+  hardware.printers = lib.mkIf printEnable {
+    ensureDefaultPrinter = ensureDefaultPrinter;
+    ensurePrinters = ensurePrinters;
   };
 }

modules/core/user.nix

@@ -51,6 +51,7 @@ in {
         "wheel" # sudo access
         "vboxusers" # Virtual Box
         "gamemode"
+        "lpadmin"
       ];
       shell = pkgs.bash;
       ignoreShellProgramCheck = true;

modules/home/xdg/desktop-entries.nix

@@ -22,7 +22,7 @@
     {
       name = "messenger";
       displayName = "Messenger";
-      url = "https://www.messenger.com/";
+      url = "https://www.facebook.com/messages/";
       iconUrl = "https://assets.stickpng.com/images/580b57fcd9996e24bc43c526.png";
       iconSha = "sha256-mQ7TAsLIWLZhun1DrJFgLkkwpqvWujhGT6Ig8Rf6vbc=";
     }