feat: Add FIDO2/U2F security key support for lock screen (#1842)

* feat: Add FIDO2/U2F security key support for lock screen

Adds hardware security key authentication (e.g. YubiKey) with two modes:
Alternative (OR) and Second Factor (AND). Includes settings UI, PAM
integration, availability detection, and proper state cleanup.

Also fixes persist:false properties being reset on settings file reload.

* feat: Add U2F pending timeout and Escape to cancel

Cancel U2F second factor after 30s or on Escape key press,
returning to password/fingerprint input.

* fix: U2F detection honors custom PAM override for non-default key paths

quickshell/Common/SettingsData.qml

@@ -494,6 +494,9 @@ Singleton {
     property bool enableFprint: false
     property int maxFprintTries: 15
     property bool fprintdAvailable: false
+    property bool enableU2f: false
+    property string u2fMode: "or"
+    property bool u2fAvailable: false
     property string lockScreenActiveMonitor: "all"
     property string lockScreenInactiveColor: "#000000"
     property int lockScreenNotificationMode: 0
@@ -985,6 +988,7 @@ Singleton {
             loadSettings();
             initializeListModels();
             Processes.detectFprintd();
+            Processes.detectU2f();
             Processes.checkPluginSettings();
         }
     }