CREATE TABLE device_tokens (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    platform TEXT NOT NULL CHECK (platform IN ('ios', 'android')),
    app TEXT NOT NULL,
    push_token TEXT NOT NULL,
    device_id TEXT,
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE UNIQUE INDEX idx_device_tokens_user_app_token ON device_tokens(user_id, app, push_token);
CREATE INDEX idx_device_tokens_user ON device_tokens(user_id);