use node: prefix for requires

mostly because code is being autogenerated by all the AI stuff using
this prefix. it's also used in the stack trace.

src/dns/hetzner.js

@@ -10,7 +10,7 @@ exports = module.exports = {
     verifyDomainConfig
 };
 
-const assert = require('assert'),
+const assert = require('node:assert'),
     BoxError = require('../boxerror.js'),
     constants = require('../constants.js'),
     debug = require('debug')('box:dns/hetzner'),