Fix PM2 UID type error by using login shell and explicit undefined

- Use su with login shell (-) to ensure clean environment
- Explicitly set uid/gid to undefined in ecosystem config
- This prevents PM2 from trying to parse string UID as integer

The error occurred because PM2 was receiving '1002' as a string
instead of an integer. By using a login shell and explicitly
setting uid/gid to undefined, PM2 won't try to switch users.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

scripts/generate-ecosystem-config.sh

@@ -49,6 +49,8 @@ module.exports = {
     kill_timeout: 3000,
     wait_ready: false,
     listen_timeout: 3000,
+    uid: undefined,
+    gid: undefined,
     env: {
       NODE_ENV: 'development',
       PORT: 3000,