enh: add toolbar and chat list context menu.

[shsiddhant]

Pull Request Summary

Add toolbar and chat list context menu with delete and edit options.

Type of Change

• New Feature
• Code Refactor

Added

1. Add a simple toolbar at the top.
2. Add a context menu to the chat list sidebar with options:
   • Edit Chat Title
   • Delete

Changed

1. Move the import button to the toolbar.
2. Move helper windows to separate module.

Checklist

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