lock screen: add lock.threatEffect toggle for fail visuals

nix/hm-module.nix

@@ -126,6 +126,11 @@ in
             default = true;
             description = "Show weather summary on the lock screen.";
           };
+          threatEffect = lib.mkOption {
+            type = lib.types.bool;
+            default = true;
+            description = "Show red vignette and chromatic aberration on failed password attempts.";
+          };
         };
         notifications = moduleOpt "notifications" {
           timeout = lib.mkOption {

shell/lock/LockSurface.qml

@@ -16,7 +16,8 @@ WlSessionLockSurface {
     property real _unlockFade: 1
 
     // Threat level: 0.0-1.0 based on fail count (5 fails = max)
-    readonly property real _threat: Math.min(1.0, root.auth.failCount / 5)
+    readonly property bool _threatEnabled: S.Modules.lock.threatEffect ?? true
+    readonly property real _threat: _threatEnabled ? Math.min(1.0, root.auth.failCount / 5) : 0
     property real _heartbeat: 0
 
     // All visual content wrapped for threat shader
@@ -321,7 +322,7 @@ WlSessionLockSurface {
     SequentialAnimation {
         id: _heartbeatAnim
         loops: Animation.Infinite
-        running: root.auth.failCount >= 3 && root.lock.secure
+        running: root._threatEnabled && root.auth.failCount >= 3 && root.lock.secure
 
         // Systole (sharp spike)
         NumberAnimation {

shell/services/Modules.qml

@@ -99,7 +99,8 @@ QtObject {
             notifications: true,
             mpris: true,
             volume: true,
-            weather: true
+            weather: true,
+            threatEffect: true
         })
     property var statsDaemon: ({
             interval: -1