🔧 chore(.env.example): update example values and add new configuration options

The .env.example file has been updated to include example values and new configuration options. The LANGFLOW_DATABASE_URL example has been updated to include both Postgres and SQLite examples. New configuration options have been added for cache type, server host, worker processes, server port, logging level, log file path, frontend directory path, whether to open the browser after starting the server, and whether to remove API keys from the projects saved in the database. These changes provide more flexibility and customization options for the application.