List trending wallets

Returns wallets ranked by trailing-window realized P&L (Polymarket-only discovery), with opaque page-cursor pagination. Each row carries window P&L, volume, distinct markets, grade, hot-streak tier, and a zero-filled daily P&L series. The underlying read model is warmed into Redis; a cold read returns 503 (warming, retry-after), never a 500 or a fabricated ranking. Polymarket-only: the read model filters platform = 'polymarket'.