```

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.
```

backend/app/models/event_media.py

@@ -39,7 +39,7 @@ class EventMedia(Base, UUIDMixin, TimestampMixin):
     description = Column(String)
 
     # Additional Metadata
-    metadata = Column(JSON, default=dict)
+    media_metadata = Column(JSON, default=dict)
 
     # Relationships
     event = relationship("Event", back_populates="media")