Remove unused SQL queries and update email template handling

- Deleted multiple unused SQL query files from the cms-service.
- Refactored email template handling in the cms-service to improve clarity and maintainability.
- Updated environment variable loading in both cms-service and lms-service to use dotenvy for better configuration management.
- Added a new .env.dev file for local development with database and SMTP configurations.
- Set default value for `certificates_enabled` in the shared common models.

shared/common/src/models.rs

@@ -999,6 +999,7 @@ mod tests {
                 primary_color: None,
                 secondary_color: None,
                 certificate_template: None,
+                certificates_enabled: true,
                 platform_name: None,
                 favicon_url: None,
                 logo_variant: None,