Feature: Add "Copy Response" action for assistant messages

[BittuBarnwal7479]

Description

It would improve the user experience to add a Copy button for assistant responses, similar to ChatGPT, Claude, and other AI platforms.

Motivation

Users often need to copy AI-generated content for use in documents, emails, code editors, or other applications. Currently, they must manually select the text.

Proposed Solution

• Add a Copy icon/button that appears on hover or beneath each assistant message.
• Copy the entire response to the clipboard with a single click.
• Show a brief confirmation (e.g., "Copied!") after a successful copy.

Benefits

• Faster workflow.
• Better usability for long responses.
• Consistent experience with other AI chat platforms.

Screenshot:

[BittuBarnwal7479]

I'd be happy to work on this and raise a PR.