feat: ✨ enable PAM fingerprint authentication for T14 Gen 6

Add PAM configuration to enable fingerprint authentication for login,
sudo, su, and xscreensaver. This makes the fingerprint interface
available in GNOME Settings and enables fingerprint unlock.

Author: bashfulrobot

lenovo/thinkpad/t14/intel/gen6/default.nix

@@ -33,4 +33,12 @@
 
   # Enable fingerprint reader support
   services.fprintd.enable = lib.mkDefault true;
+  
+  # Enable PAM fingerprint authentication for login and unlock
+  security.pam.services = {
+    login.fprintAuth = lib.mkDefault true;
+    xscreensaver.fprintAuth = lib.mkDefault true;
+    sudo.fprintAuth = lib.mkDefault true;
+    su.fprintAuth = lib.mkDefault true;
+  };
 }