InstantAdPay site skeleton: SIWE auth, live chain ledger, join links, buy flow

Zero-dependency Node server on the RM Circle pattern. Chain config lives in
the volume so the same code runs the Amoy dress rehearsal and mainnet.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

package.json

@@ -0,0 +1,9 @@
+{
+  "name": "instantadpay-site",
+  "version": "0.1.0",
+  "private": true,
+  "description": "InstantAdPay membership advertising site - immutable on-chain settlement, transparent ledger.",
+  "main": "server.js",
+  "scripts": {"start": "node server.js", "dev": "node --watch server.js"},
+  "engines": {"node": ">=20"}
+}