feat: complete saleor core extensions app with React email templates

- Order confirmation, shipped, and cancelled email templates
- Uses @react-email/components for professional HTML emails
- Sends admin and customer notifications
- Integrates with Resend for email delivery
- Webhook handlers for ORDER_CREATED, ORDER_FULFILLED, ORDER_CANCELLED
- Docker image optimized for production
- Persistent auth data storage via PVC

next.config.ts

@@ -0,0 +1,23 @@
+import path from "path";
+import { NextConfig } from "next";
+
+const config: NextConfig = {
+  output: "standalone",
+  reactStrictMode: true,
+  webpack: (config) => {
+    // When using `pnpm link` for local SDK development, webpack may resolve
+    // react/react-dom from the linked package's node_modules (different version),
+    // causing the "two Reacts" problem. Force resolution to this project's copy.
+    config.resolve = {
+      ...config.resolve,
+      alias: {
+        ...config.resolve?.alias,
+        react: path.resolve("./node_modules/react"),
+        "react-dom": path.resolve("./node_modules/react-dom"),
+      },
+    };
+    return config;
+  },
+};
+
+export default config;