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/settings/SettingsStore.js

@@ -9,6 +9,9 @@ function parse(root, jsonObj) {
 
     for (var k in SPEC) {
         if (k === "pluginSettings") continue;
+        // Runtime-only keys are never in the JSON; resetting them here
+        // would wipe values set by detection processes on every reload.
+        if (SPEC[k].persist === false) continue;
         if (!(k in jsonObj)) {
             root[k] = SPEC[k].def;
         }