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.
Introduce `EmailImage`, `EmailTemplate`, and `EmailCampaign` models for enhanced email management, including campaign tracking and one-click unsubscribe tokens. Added multilingual fields for email templates and improved accessibility with image alt text. Also adapted `Post` content fields to support translations.
Fixes: 1) Corrected `admin.py` imports for consistency and model alignment;
Extra: Refactored `choices.py` for reusable enums; restructured `models.py` for clarity and maintainability.
