feat(samples): add Node.js ecommerce demo app

- Express.js server with flag-driven checkout, catalog, promotions
- 9 flag YAML files matching the cross-language demo patterns
- package.json with flagway SDK dependency

Author: Siva

samples/ecommerce-app-node/README.md

@@ -0,0 +1,54 @@
+# FlagWay JS/TS SDK Demo — ecommerce-app-node
+
+A demo Express application showing the **@flagway/sdk** in action with a **Flag-to-Code Traceability Dashboard**.
+
+## Quick Start
+
+```bash
+# From the flagway-js monorepo root
+pnpm install
+pnpm --filter @flagway/sdk build
+pnpm --filter @flagway/loader build
+
+# Run the demo
+cd samples/ecommerce-app-node
+node server.js
+```
+
+Open [http://localhost:3001/dashboard](http://localhost:3001/dashboard)
+
+## What It Demonstrates
+
+| Feature | Endpoint | SDK Methods |
+|---------|----------|-------------|
+| Catalog features | `GET /catalog` | `isEnabled`, `getValueAs` |
+| Checkout (env-aware) | `GET /checkout/:env` | `isEnabledInEnv`, `getValueInEnv` |
+| Promotions (env-aware) | `GET /promotions/:env` | `getValueInEnv`, `getValueInEnvAs` |
+| Full traceability | `GET /flagway/state` | `exportState()` |
+| Flag inventory | `GET /flagway/flags` | `getAllFlags` |
+| Aggregate metrics | `GET /flagway/metrics` | `getAllFlags` |
+| Traceability Dashboard | `GET /dashboard` | All of the above |
+
+## Architecture
+
+```
+SDK provides data → App owns the HTTP layer
+```
+
+The entire `/flagway/state` integration is **4 lines**:
+
+```typescript
+app.get('/flagway/state', (req, res) => {
+    res.json(client.exportState());
+});
+```
+
+The dashboard consumes this endpoint to render a rich traceability UI.
+
+## Flag Files
+
+The `flags/` directory contains 10 example Flag CRDs covering:
+- Active flags with environment overrides
+- Archived flags (tombstones)
+- Expired flags past cleanup deadline
+- Snoozed migrations