feat: implement watch for monitoring chat messages

- Added a new command handler for /watch that allows users to listen to messages from a specified chat and save them according to storage rules.
- Introduced filtering options for messages using regular expressions.
- Implemented functionality to start and stop watching chats, including error handling for invalid inputs and user settings.
- Created a new utility package for message element handling related to the watch feature.
- Updated the user model to manage watched chats, including methods to add, remove, and check if a chat is being watched.

core/tftask/stream.go

@@ -32,7 +32,9 @@ func executeStream(ctx context.Context, task *Task) error {
 	})
 	var err error
 	defer func() {
-		task.Progress.OnDone(ctx, task, err)
+		if task.Progress != nil {
+			task.Progress.OnDone(ctx, task, err)
+		}
 	}()
 	if err = errg.Wait(); err != nil {
 		return err