fix(notifications): dismiss popups when senders close notifications

When a sender calls CloseNotification (per freedesktop spec) for a
persistent notification (expire-timeout=0), the onDropped handler
removed the wrapper from internal arrays but did not dismiss the
visible popup. The popup remained on screen forever for non-critical
notifications like YubiKey touch prompts.

Set wrapper.popup=false in onDropped so the popup exits via the
normal signal chain. This is minimal; it does not change timeout
handling, queue management, or the isPersistent marker.

Also reverts the previous workaround that special-cased non-critical
expireTimeout=0 to use DMS timeout. Upstream spec-correct behavior
is to honor the sender timeout, and fix the dismissal bug instead.

Closes #2814

Author: atimofeev

quickshell/Services/NotificationService.qml

@@ -888,6 +888,11 @@ Singleton {
                     return;
                 }
 
+                // Dismiss visible popup when sender closes the notification
+                // (e.g. YubiKey sends CloseNotification after touch).
+                // Without this, expireTimeout=0 popups stay visible forever.
+                wrapper.popup = false;
+
                 const groupKey = getGroupKey(wrapper);
                 const remainingInGroup = root.notifications.filter(n => getGroupKey(n) === groupKey);