Let AIwire it up.

You are my developer. Help me accept crypto payments on my website with blockwallets (customers pay in USDT, USDC, BTC and 14 other coins; I’m credited in US dollars).

## About me
- My site is built with: I’m not sure. Look at my project first, tell me what it is built with, then start.
- How I want to get paid: Create a bill at checkout and redirect the customer to the blockwallets payment page; when the money arrives, blockwallets calls my server and I mark the order as paid and ship it.
- I’m not a programmer. For every step, tell me which files you changed and what I need to do (for example where to put environment variables). Don’t change too much at once.
- AGENTS.md in the project root holds the blockwallets integration rules; read it first, and read https://blockwallets.io/llms-full.txt for details.

## Read the docs first; don’t guess the API from memory
- Full integration docs (Markdown): https://blockwallets.io/llms-full.txt
- Integration rules and common mistakes: https://blockwallets.io/agents.md
- If the site already uses Cryptomus, NOWPayments or Coinbase Commerce, switch it to the matching compatible API instead of rewriting: https://blockwallets.io/docs/migrate.md?lang=en
- If you can’t open a link, tell me and I’ll paste the content.

## Key points (where integrations usually go wrong)
1. Every endpoint is POST + JSON on https://blockwallets.io. Headers: merchant = the merchant UUID, sign = md5(base64(request body) + API key). Sign the exact JSON string you send; do not re-serialize after signing.
2. Create a bill with POST /v1/payment. Required: amount (a string with up to two decimals, e.g. "42.00"), currency ("USD"), order_id (my order number: letters, digits, - and _, up to 100 characters). Also pass url_callback (the webhook URL) and url_success (where the customer returns after paying). Redirect the customer to result.url.
3. Calling again with the same order_id returns the same bill, so retries are safe and never create a second bill.
4. Webhook signatures must be verified: parse the webhook JSON, drop the sign field, re-encode the rest the way PHP json_encode does (compact, non-ASCII kept, / escaped as \/), then md5(base64(encoded) + API key) must equal sign. Forgetting to escape / is the most common mistake.
5. Mark the order paid only when status is paid or paid_over, using payment_amount_usd. The same webhook can arrive more than once: deduplicate by uuid + status. Reply with a 2xx status once handled.
6. Keep the merchant ID and API key in environment variables (e.g. BW_MERCHANT, BW_API_KEY); never hard-code them or commit them. Add the domain of the webhook URL under “Website domains” on the dashboard’s “Developers › Integration & keys” page first.
7. Get everything working with the Test credentials first (testnets, no real money); switch to Live only after I confirm.

## When you’re done, check each item and tell me the result
- [ ] Create a test bill with the Test credentials and get the payment page link (result.url)
- [ ] Open the payment page and click “Simulate payment” → full amount
- [ ] My server receives a webhook with status paid and the signature verifies
- [ ] The matching order is marked as paid
- [ ] The same webhook arriving again (resend it from the dashboard’s “Developers › Webhook log”, or POST /v1/payment/resend) does not ship twice

If any item fails, tell me where it’s stuck and the exact error message before changing anything else.