feat(x402-demo): public deploy config + PORT from env

examples/x402-demo/Dockerfile

@@ -0,0 +1,18 @@
+# x402 demo server — public 402 paywall ($0.001 USDC on Base Sepolia).
+# Deployed as a CodeSpar example API so agents can pay a real 402 resource.
+# Env (set in Railway, NOT baked in): SERVER_ADDRESS (payee 0x), FACILITATOR_URL.
+# Do NOT copy .env into the image — it holds the example CLIENT_PRIVATE_KEY.
+FROM node:22-slim
+WORKDIR /app
+
+COPY package.json ./
+# Full install (not --omit=dev): the server runs via `tsx`, a devDependency.
+RUN npm install --no-audit --no-fund
+
+COPY server.ts ./
+
+# Railway injects PORT; the server reads process.env.PORT (fallback 4021).
+ENV PORT=4021
+EXPOSE 4021
+
+CMD ["npx", "tsx", "server.ts"]

examples/x402-demo/railway.json

@@ -0,0 +1,14 @@
+{
+  "$schema": "https://railway.com/railway.schema.json",
+  "build": {
+    "builder": "DOCKERFILE",
+    "dockerfilePath": "Dockerfile",
+    "watchPatterns": ["examples/x402-demo/**"]
+  },
+  "deploy": {
+    "healthcheckPath": "/api/health",
+    "healthcheckTimeout": 10,
+    "restartPolicyType": "ON_FAILURE",
+    "restartPolicyMaxRetries": 3
+  }
+}

examples/x402-demo/server.ts

@@ -88,7 +88,7 @@ app.get("/api/premium-analysis", (_req, res) => {
   });
 });
 
-const PORT = 4021;
+const PORT = Number(process.env.PORT) || 4021;
 app.listen(PORT, () => {
   console.log(`\n  x402 Demo Server running on http://localhost:${PORT}`);
   console.log(`  Network: Base Sepolia (eip155:84532)`);