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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This commit introduces the `Guest` model to manage event guests, including their details, status, RSVP tracking, and relationships with events and users. It also supports features like invitation handling, guest statuses, and guest-to-gift associations. This forms the foundation for handling guest-related functionalities in the backend.
