ALTER TABLE users
    ADD COLUMN moderation_status ENUM('pending','approved','rejected') NOT NULL DEFAULT 'pending' AFTER qx_status,
    ADD COLUMN moderation_note VARCHAR(500) NULL AFTER moderation_status,
    ADD COLUMN reviewed_by BIGINT UNSIGNED NULL AFTER moderation_note,
    ADD COLUMN reviewed_at DATETIME NULL AFTER reviewed_by,
    ADD KEY idx_users_moderation_status (moderation_status),
    ADD CONSTRAINT fk_users_reviewed_by FOREIGN KEY (reviewed_by) REFERENCES admins(id) ON DELETE SET NULL;