Create POST /api/v1/members/me/watched-episodes/batch #1390

Implement a secured POST endpoint.

• Payload: Accepts a JSON array of UUID (representing episode_ids). Limit the array size (e.g., max 50 items) to prevent abuse.

• Logic: Query the MemberFollowEpisode table using an IN (...) clause filtered by the current member_id.

• Response: Return a simple JSON array of UUID containing only the IDs from the request payload that the user has actually watched.