fix(notifications): prevent non-critical expireTimeout=0 from persisting forever

Notifications with expire-timeout=0 (freedesktop spec: never expire)
now only persist indefinitely when urgency is Critical. Non-critical
notifications with expire-timeout=0 (e.g. YubiKey/pam_u2f touch prompts)
fall back to the DMS per-urgency timeout instead of persisting until
manually dismissed.

Root cause: the timer interval honored appTimeout >= 0, treating
expire-timeout=0 literally. Combined with _initWrapperPersistence
marking timeoutMs===0 as persistent, these notifications were never
auto-dismissed, never destroyed, and never removed from the queue.

Fixes: YubiKey/pam_u2f touch notifications, and any other sender that
uses expire-timeout=0 for non-critical notifications.

Author: atimofeev

quickshell/Services/NotificationService.qml

@@ -773,8 +773,12 @@ Singleton {
                     return 5000;
                 // expireTimeout is in milliseconds; -1 defers to our settings.
                 const appTimeout = wrapper.notification.expireTimeout;
-                if (appTimeout >= 0)
+                if (appTimeout > 0)
                     return Math.round(appTimeout);
+                // expire-timeout 0 means "never expire" per freedesktop spec.
+                // Only honor for Critical urgency; non-Critical falls through to DMS timeout.
+                if (appTimeout === 0 && wrapper.urgency === NotificationUrgency.Critical)
+                    return 0;
                 switch (wrapper.urgency) {
                 case NotificationUrgency.Low:
                     return SettingsData.notificationTimeoutLow;