Batch account value (current NAV) for up to 50 wallets

Resolves the COMPLETE mode-aware account value for each wallet in `users` (≤50) — perp equity across every dex + spot + vault + staking, unrealized PnL counted once, same source as `/v1/portfolio` and `/v1/me/stats`. Per-address failures degrade to `valueUsd: null` + a `note` instead of failing the batch. Over 50 addresses → 400; page client-side. v1 returns CURRENT STATE only (valueUsd / buckets / unrealizedPnlUsd / accountMode) — lifetime netDeposits / realizedPnl are deferred (node-local history is windowed). Total PnL for a fund is best derived business-side as Σ valueUsd − Σ netDeposits once lifetime deposits are available.