CREATE TABLE users (
  id SERIAL PRIMARY KEY,
  username TEXT UNIQUE NOT NULL,
  password TEXT NOT NULL,
  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE TABLE sessions (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id INTEGER NOT NULL REFERENCES users(id),
  expires_at TIMESTAMPTZ NOT NULL,
  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);