add feed generators for Google Merchant, Amazon Seller, Yandex Market, and Yandex Products. Includes a shared base class (`BaseFeedGenerator`) for common functionality, such as product retrieval and validation. Each generator supports format-specific output and handles platform-specific requirements.
This change simplifies the creation of product feeds for multiple marketplaces.
Fixes: 1) Add exception handling for invalid image file dimensions in `validators.py`;
Extra: 1) Update settings categories to include new system options; 2) Improve code clarity in `backup_task` and `validators.py`.
Fixes: 1) Apply `--omit` filter for test coverage reports to exclude unnecessary files; 2) Replace `services_data` volume mounts with named Docker volumes for consistency and cleanup (e.g., `postgres-data`, `redis-data`);
Extra: 1) Remove `services_data` from `.gitignore`, Docker-related cleanup in uninstall scripts; 2) Simplified related files removal scripts for Unix and Windows; 3) Minor adjustments in documentation comments.
