function log_action($task_id, $user_id, $action, $comment = null) {
    $pdo = Database::connect();
    $stmt = $pdo->prepare("
        INSERT INTO logs (task_id, user_id, action, comments) 
        VALUES (?, ?, ?, ?)
    ");
    $stmt->execute([$task_id, $user_id, $action, $comment]);
}