fix(lockscreen): drop noctalia-lock PAM fallback, prefer su for password

Author: Ly-sec

src/shell/lockscreen/lock_screen.cpp

@@ -716,13 +716,8 @@ void LockScreen::scheduleAutoAuthentication() {
 bool LockScreen::fingerprintAuthLikelyAvailable() { return fprintd::isAvailable(); }
 
 std::string LockScreen::passwordPamService() {
-  if (!fingerprintAuthLikelyAvailable()) {
-    return "login";
-  }
-  if (PamAuthenticator::pamServiceExists("noctalia-lock")) {
-    return "noctalia-lock";
-  }
-  if (PamAuthenticator::pamServiceExists("su")) {
+  // When login stacks pam_fprintd before pam_unix (e.g. NixOS fprintAuth), use su if present.
+  if (fingerprintAuthLikelyAvailable() && PamAuthenticator::pamServiceExists("su")) {
     return "su";
   }
   return "login";