update payment and add magic spend mention

Author: youssefea

docs/base-account/guides/accept-payments.mdx

@@ -12,6 +12,7 @@ USDC on Base is a fully-backed digital dollar that settles in seconds and costs
 * **Any user can pay** – works with every Base Account (smart-wallet) out of the box.
 * **USDC, not gas** – you charge in dollars; gas sponsorship is handled automatically.
 * **Fast** – most payments confirm in <2 seconds on Base.
+* **Coinbase** – users can pay with their USDC balance on Coinbase by default.
 * **No extra fees** – you receive the full amount.
 
 <Warning>

docs/base-account/improve-ux/magic-spend.mdx

@@ -74,6 +74,13 @@ export function SendButton({ address }: Props) {
 3. Reads `auxiliaryFunds.supported` for the Base chain (`8453`).
 4. Enables the button when MagicSpend is available; otherwise shows “Insufficient Balance”.
 
+## Base Pay integrates Magic Spend by default
+
+Thanks to [Magic Spend](/base-account/improve-ux/magic-spend), [Base Pay](/base-account/guides/accept-payments) allows users to pay with their USDC balance on Coinbase by default.
+
+<div style={{ display: 'flex', justifyContent: 'center' }}>
+  <img src="/images/base-account/CoinbaseSpend.png" alt="Pay with Coinbase on Base Account" style={{ width: '300px', height: 'auto' }} />
+</div>
 ---
 
 ## Next steps