Add user feedback for clipboard copy failures

[Sharanyaaa08]

@Durgeshwar-AI ,

Description

Implemented user feedback for failed image copy actions in the PDF to PNG results section.

Changes Made

• Added error handling for clipboard copy failures.
• Added a visible error message when image copy fails.
• Kept existing success feedback when copy succeeds.
• Logged copy errors for debugging purposes.

Before

• Copy failures were only logged in the console.
• Users received no visible feedback.

After

• Users now see:
  "Unable to copy image. Please download it instead."
• Success feedback ("Copied!") remains unchanged.

Fixes #347

[vercel]

@Sharanyaaa08 is attempting to deploy a commit to the Durgeshwar's projects Team on Vercel.

A member of the Team first needs to authorize it.

[Durgeshwar-AI]

@Sharanyaaa08 Use the sonner package which is installed to show the feedbacks