Announcements: Show snackbar on event and enhanced comment notification messages

lib/screens/announcements/announcement_comments_section.dart

@@ -5,6 +5,7 @@ import '../../models/announcement_comment.dart';
 import '../../providers/announcements_provider.dart';
 import '../../providers/profile_provider.dart';
 import '../../utils/app_time.dart';
+import '../../utils/snackbar.dart';
 import '../../widgets/profile_avatar.dart';
 
 /// Inline, collapsible comments section for an announcement card.
@@ -43,6 +44,7 @@ class _AnnouncementCommentsSectionState
             body: text,
           );
       _controller.clear();
+      if (mounted) showSuccessSnackBar(context, 'Comment posted.');
     } on AnnouncementNotificationException {
       // Comment was posted; only push notification delivery failed.
       _controller.clear();