enh: add lazy loading of texts and make them scrollable.

[shsiddhant]

Pull Request Summary

Adds lazy loading of texts and makes them scrollable.

Type of Change

Choose one or more:

• New Feature

Changes

1. Modify message service get_messages to accept limit and offset.
2. Modify MessageList model:
   • Accept message service and limit as parameters instead of message list.
   • Add canFetchMore and fetchMore methods for lazy loading of texts.
3. Modify ChatView and MainWindow models accordingly.

Checklist

• Code runs without errors
• Code style and lint checks passed