Fix Passenger ESM incompatibility — add server.cjs CJS wrapper

Passenger's node-loader uses require() which cannot load ES modules.
server.cjs is a CommonJS shim that bridges into server.js via dynamic import().

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server.cjs

@@ -0,0 +1,7 @@
+// CommonJS wrapper for Phusion Passenger.
+// Passenger's node-loader uses require(), which cannot load ES modules directly.
+// This shim bridges into the ESM entry point via dynamic import().
+import('./server.js').catch((err) => {
+  console.error(err);
+  process.exit(1);
+});