List recent feedback sessions

user_feedback table is populated; sessions grouping correctly

SELECT f.session_id, u.username, COUNT(*) AS messages,
       MIN(f.created_at) AS started_at, MAX(f.created_at) AS last_at
FROM telegram_system.user_feedback f
LEFT JOIN telegram_bot.users u ON u.telegram_id = f.telegram_user_id
GROUP BY f.session_id, f.telegram_user_id
ORDER BY started_at DESC
LIMIT 20;