CREATE TABLE report_messages (
    id         UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    report_id  UUID NOT NULL REFERENCES reports(id) ON DELETE CASCADE,
    role       VARCHAR(10) NOT NULL CHECK (role IN ('user', 'assistant')),
    content    TEXT NOT NULL,
    status     VARCHAR(10) NOT NULL DEFAULT 'done' CHECK (status IN ('done', 'generating', 'error')),
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);