feat: add gpg agent

Modules/System/Application/Special-Applications/default.nix

@@ -7,5 +7,6 @@
   imports = [
     ./flatpak.nix
     ./wireshark.nix
+    ./gpg.nix
   ];
 }

Modules/System/Application/Special-Applications/gpg.nix

@@ -0,0 +1,64 @@
+# GPG (System Module)
+#
+# Provides:
+#   - GnuPG installation (gpg, pinentry)
+#   - gpg-agent system service (with optional SSH support)
+#   - Desktop secrets integration (gnome-keyring, seahorse)
+#
+# Options:
+#   - enable          -> Enable GnuPG system module
+#   - enableSSHSupport -> Enable SSH agent emulation in gpg-agent
+#   - enableSeahorse   -> Enable Seahorse (GUI key manager)
+#   - pinentry.package -> Pinentry package (default: pkgs.pinentry-all)
+#
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.nyx-module.system.gpg;
+in {
+  options.nyx-module.system.gpg = {
+    enable = lib.mkEnableOption "Enable GnuPG (system module)";
+
+    enableSSHSupport = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      description = ''
+        Enable SSH agent emulation support in gpg-agent.  
+        This allows you to use your GPG keys for SSH authentication.
+      '';
+    };
+
+    enableSeahorse = lib.mkEnableOption "Enable Seahorse (GUI key manager)";
+
+    pinentry.package = lib.mkOption {
+      type = lib.types.package;
+      default = pkgs.pinentry-all;
+      description = ''
+        The pinentry package to use.  
+        By default, `pkgs.pinentry-all` is installed, which includes
+        all common backends (tty, curses, gtk2, qt, gnome3).
+      '';
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    # Enable gpg-agent with optional SSH support
+    programs.gnupg.agent = {
+      enable = true;
+      enableSSHSupport = cfg.enableSSHSupport;
+    };
+
+    # Enable gnome-keyring (for desktop secret storage)
+    services.gnome.gnome-keyring.enable = true;
+
+    # Optional GUI for secrets management
+    programs.seahorse.enable = cfg.enableSeahorse;
+
+    # Base packages + user-supplied pinentry
+    environment.systemPackages = with pkgs; [
+      gnupg
+      gnome-keyring
+      cfg.pinentry.package
+    ];
+  };
+}