Normalized Polymarket settlements and redeems for public wallets

Returns canonical automatic Loss and explicit Redeem activity from the local tracked-wallet projection. A losing Redeem replaces the matching automatic Loss while inheriting its authoritative economics and metadata; winning and invalid Redeem legs remain distinct. Raw `/polymarket/data/activity` and `/polymarket/data/closed-positions` remain verbatim passthroughs. Automatic Loss is cashflow-neutral (`amountUsd=null`); Redeem carries the authoritative payout.