Rename metadata fields for clarity and fix imports.
Updated metadata-related field names across models to improve clarity and consistency (e.g., `metadata` to `media_metadata` and `notification_metadata`). Fixed an error in `guest_gifts` metadata reference and added a proper imports initialization in `__init__.py` for all models.
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Introduced new database models to handle email templates, activity logs, and notification logs, including relevant enums and utilities. Updated ER diagram to reflect new relationships and attributes, enhancing event tracking and notification management capabilities.
