CREATE TABLE user_preferences (
    user_id          uuid PRIMARY KEY REFERENCES users(id) ON DELETE CASCADE,
    reader_mode      text NOT NULL DEFAULT 'single'
        CHECK (reader_mode IN ('single', 'continuous')),
    reader_page_gap  text NOT NULL DEFAULT 'none'
        CHECK (reader_page_gap IN ('none', 'small', 'medium', 'large')),
    updated_at       timestamptz NOT NULL DEFAULT now()
);