fix(clipboard): guard clipboard access on insecure context

[techykaif]

What this changes

Fixes #140 by checking for clipboard API support before attempting to write a shared link.

On browsers or origins where navigator.clipboard is unavailable, the UI now shows an error toast instead of throwing synchronously. HTTPS and localhost behavior remains unchanged.

Type of change

• New public place(s)
• New or updated benefit guide
• New or updated resource link
• Code or fix
• Docs

Proof (required for new public places)

Not applicable. This PR does not add or modify any public places.

Checklist

• The site hosts no copyrighted files; resource and paper changes are links only.
• No em dashes in any copy.

[vercel]

@techykaif is attempting to deploy a commit to the studentsuite Team on Vercel.

A member of the Team first needs to authorize it.