fix: skip migrations gracefully when drizzle folder missing (worker deployments)

Commit notes

The migrate-deploy.ts script was throwing an error when the drizzle migration journal was not found. This caused worker deployments to fail when: 1. The .dockerignore excludes the drizzle/ folder 2. The worker service uses the same railway.json as the API

Now the script gracefully exits with success (exit code 0) when the migration journal is not found, logging a warning message. This is expected behavior for worker deployments which don't need to run migrations - only the API service should handle migrations.

Co-authored-by: armin.naimi <[email redacted]>