Replace WYSIWYG editor with Markdown editor across all relevant models and admin fields. Add utilities for rendering and stripping markdown. Adjust serializers, views, and templates to support markdown content. Introduce `PastedImage` model and upload endpoint for handling inline image uploads in markdown.
This change simplifies content formatting while enhancing flexibility with markdown support.
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.
