refactor: migrate from pnpm workspaces to single-package structure with shared types

client/next.config.js

@@ -0,0 +1,9 @@
+/** @type {import('next').NextConfig} */
+const nextConfig = {
+  reactStrictMode: true,
+  experimental: {
+    serverActions: true
+  }
+};
+
+module.exports = nextConfig;