migrate Tasks::Fa::EnqeueuUnstannedOkPostsTask to interruptable task mechanism

rake/fa.rake

@@ -38,8 +38,9 @@ namespace :fa do
   end
 
   task enqueue_unscanned_ok_posts: %i[set_logger_stdout environment] do
-    start_at = ENV["start_at"]&.to_i
-    Domain::Fa::EnqueueUnscannedOkPosts.new(start_at: start_at).run
+    start_at = ENV["start_at"]
+    start_at = start_at.to_i if start_at && start_at != "last"
+    Tasks::Fa::EnqueueUnscannedOkPostsTask.new(start_at: start_at).run
   end
 
   desc "enqueue waiting users"