Report Message using Flag and Review

Introduce a Report Message feature using a Flag and Review workflow. Users can report messages, which are flagged for moderator review without being blocked or removed.

The status of flagged messages should update in real-time for both sender and receiver, allowing the UI to indicate that the message is under review.

This feature will enhance in-app moderation and user safety while complementing the upcoming core moderation product, providing a smooth and effective reporting experience.