Link the calculator with the keyboard

[anujsharma8d]

📝 Description

This PR links the calculator with the keyboard. Now the user can use calculator with keyboard also.

🔗 Linked Issue

Closes #555

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📋 Contribution Checklist

• My code strictly adheres to the project guidelines (Standard library only, procedural code, clean spacing).
• I have verified that my files are placed in the correct directory.
• I have tested my changes thoroughly on my local machine.
• GSSoC 2026: I have been formally assigned to this issue and noted it above.

[vercel]

@anujsharma8d is attempting to deploy a commit to the Anuj's projects Team on Vercel.

A member of the Team first needs to authorize it.

[anujsharma8d]

@steam-bell-92
Kindly review.

[github-actions]

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