v1.5

feat(backend): enhance WordPress plugin and database commands

- Bump plugin version to 1.5 and add a ping endpoint for connectivity testing.
- Improve error handling in the WordPress client for export and import operations, including detailed responses for API errors.
- Update export and import commands to validate file sizes and handle potential errors more gracefully.
- Refactor CouchDB and MySQL/MariaDB command logic for better clarity and reliability.
- Enhance UI to include connection testing for WordPress and local databases, providing user feedback on potential issues.
- Streamline export and import workflows with improved progress tracking and error messages.