Implement the request detail / pay page

[iexwr]

Context

src/pages/Request.tsx is a placeholder. This is the public page a payer lands on from a shared link.

Acceptance criteria

• Fetch request by id from the API/contract; show payee, asset, amount, memo, and a status badge (Open/Paid/Cancelled/Expired).
• When Open, show a Pay button that prompts the wallet, signs, and submits the pay call.
• Disabled / replaced-by-receipt state when already Paid.
• Handle not-found and load states.

Technical notes

• Use useParams() for :id.
• Reuse useWallet for signing.

Testing

• Component test for Open and Paid states with a mocked backend.