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/settings/SettingsSpec.js

@@ -355,6 +355,7 @@ var SPEC = {
     lockAtStartup: { def: false },
     enableFprint: { def: false },
     maxFprintTries: { def: 15 },
+    lockFaillockSupported: { def: false, persist: false },
     fprintdAvailable: { def: false, persist: false },
     lockFingerprintCanEnable: { def: false, persist: false },
     lockFingerprintReady: { def: false, persist: false },