1. Add finalResult property to SpeechRecognitionResult class
- Distinguish between real-time and final recognition results
- Update factory methods, toString, equals, and hashCode
- Update toMap and fromMap methods
2. Update YxAsrService to support finalResult flag
- Add finalResult parameter to _sendResult method
- Mark final results with finalResult: true
- Keep real-time results as finalResult: false (default)
3. Remove unused methods to clean up codebase
- Remove unused _toggleRecording method
- Remove unused _updateTextController method
- Clean up orphaned comments
These fixes resolve linter errors and ensure proper text appending functionality.