[Bug] Math.random() used for SIWE nonce in Wagmi setup example — not cryptographically secure

[zakaziko86]

Description

The Wagmi integration setup example uses Math.random() to generate
a SIWE (Sign-In With Ethereum) nonce:

const clientNonce =
  Math.random().toString(36).substring(2, 15) +
  Math.random().toString(36).substring(2, 15);

Math.random() is not cryptographically secure and should never be
used for SIWE nonces. A predictable nonce can be exploited to perform
replay attacks.

Impact

• Developers copying this example will implement insecure SIWE flows
• Predictable nonces can be exploited for replay attacks
• Contradicts the authenticate-users guide which already uses
  crypto.randomUUID()

Suggested Fix

Replace with crypto.randomUUID():

const clientNonce = crypto.randomUUID();

✅ Cryptographically secure (Web Crypto API)
✅ Available in all modern browsers and Node.js 14.17+
✅ Consistent with existing authenticate-users guide

References

• Related PR: fix(docs): replace Math.random() nonce with crypto.randomUUID() in Wagmi setup example #1398
• Related issue: fix(docs): replace Math.random() nonce with crypto.randomUUID() in Wagmi integration example #1390