clear toast on tap

this adds a generator showDismissibleSnackBar which by default allows
tapping to clear snack bar toasts. all SnackBar properties are still
available and the

all callers should now use showDismissibleSnackBar() instead of calling
ScaffoldMessenger.of(context).showSnackBar(SnackBar())

lib/screens/map_screen.dart

@@ -29,6 +29,7 @@ import 'chat_screen.dart';
 import 'contacts_screen.dart';
 import '../widgets/repeater_login_dialog.dart';
 import '../widgets/room_login_dialog.dart';
+import '../helpers/snack_bar_builder.dart';
 import 'repeater_hub_screen.dart';
 import 'settings_screen.dart';
 import 'line_of_sight_map_screen.dart';
@@ -1659,7 +1660,10 @@ class _MapScreenState extends State<MapScreen> {
                 );
                 await connector.refreshDeviceInfo();
                 if (!mounted) return;
-                messenger.showSnackBar(SnackBar(content: Text(successMsg)));
+                showDismissibleSnackBar(
+                  messenger.context,
+                  content: Text(successMsg),
+                );
               },
             ),
             ListTile(
@@ -1681,8 +1685,9 @@ class _MapScreenState extends State<MapScreen> {
     required String flags,
   }) async {
     if (!connector.isConnected) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(content: Text(context.l10n.map_connectToShareMarkers)),
+      showDismissibleSnackBar(
+        context,
+        content: Text(context.l10n.map_connectToShareMarkers),
       );
       return;
     }
@@ -2271,8 +2276,9 @@ class _MapScreenState extends State<MapScreen> {
                           _points.clear();
                           _polylines.clear();
                         });
-                        ScaffoldMessenger.of(context).showSnackBar(
-                          SnackBar(content: Text(l10n.map_pathTraceCancelled)),
+                        showDismissibleSnackBar(
+                          context,
+                          content: Text(l10n.map_pathTraceCancelled),
                         );
                       },
                       tooltip: l10n.common_cancel,