docs: add x402 kora demo

docs/x402/demo/api/package.json

@@ -0,0 +1,22 @@
+{
+  "name": "api",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "start": "tsx src/api.ts"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "packageManager": "[email protected]",
+  "dependencies": {
+    "dotenv": "^17.2.2",
+    "express": "^5.1.0",
+    "x402-express": "^0.6.1"
+  },
+  "devDependencies": {
+    "@types/node": "^24.5.2",
+    "tsx": "^4.20.5"
+  }
+}

docs/x402/demo/api/src/api.ts

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+import express from "express";
+import { Network, paymentMiddleware, SolanaAddress } from "x402-express";
+import { config } from "dotenv";
+import path from "path";
+
+config({ path: path.join(process.cwd(), '..', '.env') });
+
+type Resource = `${string}://${string}`;
+
+const API_PORT = process.env.API_PORT || 4021;
+const FACILITATOR_URL = process.env.FACILITATOR_URL as Resource || "http://localhost:3000";
+const NETWORK =  (process.env.NETWORK || "solana-devnet") as Network;
+const KORA_SIGNER_ADDRESS = process.env.KORA_SIGNER_ADDRESS as SolanaAddress;
+
+if (!KORA_SIGNER_ADDRESS) {
+  throw new Error("KORA_SIGNER_ADDRESS is not set");
+}
+
+const app = express();
+
+app.use(
+  paymentMiddleware(
+    KORA_SIGNER_ADDRESS,
+    {
+      "GET /protected": {
+        price: "$0.0001",
+        network: NETWORK,
+      },
+    },
+    {
+      url: FACILITATOR_URL,
+    }
+  ),
+);
+
+app.get("/protected", (req, res) => {
+  res.json({
+    message: "Protected endpoint accessed successfully",
+    timestamp: new Date().toISOString(),
+  });
+});
+
+app.get("/health", (req, res) => {
+  res.json({ status: "ok" });
+});
+
+
+app.listen(API_PORT, () => {
+  console.log(`Server listening at http://localhost:${API_PORT}`);
+});
+
+// curl -X GET http://localhost:4021/protected
+// curl -X GET http://localhost:4021/health

docs/x402/demo/client/package.json

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+{
+  "name": "kora-demo-client",
+  "version": "1.0.0",
+  "description": "",
+  "scripts": {
+    "start": "tsx src/index.ts",
+    "setup": "tsx src/setup.ts"
+  },
+  "keywords": [
+    "solana",
+    "kora",
+    "client"
+  ],
+  "author": "Solana Foundation",
+  "license": "MIT",
+  "packageManager": "[email protected]",
+  "dependencies": {
+    "dotenv": "^17.2.0",
+    "gill": "^0.11.0",
+    "x402-fetch": "^0.6.0"
+  },
+  "devDependencies": {
+    "@types/node": "^24.0.13",
+    "tsx": "^4.20.5",
+    "typescript": "^5.8.3"
+  }
+}