create table if not exists notification_messages (
  id serial primary key,
  title varchar(200) not null,
  body text not null,
  category varchar(60) not null default 'general',
  source varchar(80) not null default 'system',
  priority varchar(20) not null default 'normal',
  is_read boolean not null default false,
  read_at timestamptz null,
  metadata_json jsonb not null default '{}'::jsonb,
  created_at timestamptz not null default now(),
  updated_at timestamptz not null default now()
);

create index if not exists idx_notification_messages_unread_created_at
  on notification_messages (is_read, created_at desc, id desc);