style(DialogWidget): remove backdrop filter for non-modal overlay

- Updated the non-modal dialog overlay to have no backdrop filter, enhancing visual clarity.
- Set the modal property to false in MessagesDialog to ensure proper dialog behavior.

frontend/src/components/DialogWidget.vue

@@ -195,6 +195,7 @@ export default {
 
 .dialog-overlay.non-modal {
   background: transparent;
+  backdrop-filter: none;
   pointer-events: none;
 }
 

frontend/src/components/falukant/MessagesDialog.vue

@@ -5,6 +5,7 @@
     :title="'falukant.messages.title'"
     :isTitleTranslated="true"
     icon="falukant/messages24.png"
+    :modal="false"
   :buttons="[
     { text: 'falukant.messages.markAllRead', action: 'markAll' },
     { text: 'message.close', action: 'close' }
@@ -363,4 +364,3 @@ export default {
 .pagination button { padding: .25em .6em; }
 .pagination input[type="number"] { width: 4em; text-align: right; }
 </style>
-