fix: analyzer warning in quicklinks_listview.dart

Fix the analyzer warning about using 'BuildContext' across async gaps in `lib/components/drawer/quicklinks_listview.dart`.

* Convert `onLongPress` to an async function.
* Replace the `.then()` call with `await` for `Clipboard.setData`.
* Add a check for `mounted` before calling `ScaffoldMessenger.of(context).showSnackBar`.

---

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lib/components/drawer/quicklinks_listview.dart

@@ -31,15 +31,15 @@ class QuicklinksListView extends StatelessWidget {
               overflow: TextOverflow.ellipsis,
             ),
             onTap: () => openUrl(source.url),
-            onLongPress: () {
+            onLongPress: () async {
               Navigator.pop(context);
-              Clipboard.setData(ClipboardData(text: url)).then((_) {
-                ScaffoldMessenger.of(context).showSnackBar(
-                  SnackBar(
-                      content: Text(
-                          AppLocalizations.of(context)!.copiedToClipboard)),
-                );
-              });
+              await Clipboard.setData(ClipboardData(text: url));
+              if (!mounted) return;
+              ScaffoldMessenger.of(context).showSnackBar(
+                SnackBar(
+                    content: Text(
+                        AppLocalizations.of(context)!.copiedToClipboard)),
+              );
             },
           );
         }).toList(),