fix(lock): Restore system PAM fallback, faillock support, and auth feedback

- Re-add loginConfigWatcher so installs can still fall through to
  /etc/pam.d instead of the bundled PAM assets
- Add login-faillock bundled PAM asset at runtime. Use it as the bundled fallback when dankshell config is absent
- Fix invalid bare property writes (u2fPending, u2fState, unlockInProgress,
  state) in Pam.qml
- Improve lockscreen auth feedback

quickshell/Common/SettingsData.qml

@@ -505,6 +505,7 @@ Singleton {
 
     property bool enableFprint: false
     property int maxFprintTries: 15
+    property bool lockFaillockSupported: false
     property bool fprintdAvailable: false
     property bool lockFingerprintCanEnable: false
     property bool lockFingerprintReady: false