Turn on refundsfor AI payments.

You are integrating x402refunds.com into a repo with X-402 paywalled endpoints.

Do these steps exactly (end-to-end):

0) Find every X-402 paywalled endpoint in this repo
   - Identify all routes/handlers that can return HTTP 402 Payment Required for X-402.
   - These are the endpoints we mean by "paid endpoints" (exclude payment/signature/facilitator plumbing endpoints).

Apply the steps below to paywalled endpoints on BOTH Base and Solana.

1) Add a Link header with your refund email (refund contact) to ALL paywalled endpoints
   - Add this on every response those endpoints produce: both 200 and 402.
   - Apply it to every method used (GET, POST, etc.).
     Link: <mailto:refunds@yourdomain.com>; rel="https://x402refunds.com/rel/refund-contact"
   - The <...> target should be mailto:refunds@yourdomain.com
   - This must be the email the owner wants to receive refund requests at.

2) Add a Link header advertising the refund-request filing URL on paid 200 responses
   - On every paywalled endpoint, when returning 200 OK after a paid request, include:
     Link: <https://api.x402refunds.com/v1/refunds>; rel="https://x402refunds.com/rel/refund-request"; type="application/json"
   - Return this on successful paid 200 responses only.

3) Deploy + test (required)
   - Deploy to production.
   - Test at least one paywalled endpoint:
     - Unpaid request => 402 response MUST include the refund-contact Link header.
     - Paid request => 200 response MUST include refund-contact + refund-request Link headers.

Important:
If you do not know the correct refund contact email, ask your owner for it. Do not guess.