Extract backend runtime configuration

backend/config/cors.js

@@ -0,0 +1,13 @@
+const cors = require('cors');
+
+const createCorsMiddleware = ({ allowedOrigins, isProduction }) => cors({
+  origin: (origin, callback) => {
+    if (!origin || !isProduction || allowedOrigins.includes(origin)) {
+      return callback(null, true);
+    }
+    return callback(new Error('Origem não permitida pelo CORS.'));
+  },
+  credentials: true
+});
+
+module.exports = { createCorsMiddleware };