feat: add manual USDT account rebalance

[jackhai9]

Summary

• add an inline manual USDT rebalance action after global futures positions and open orders remain empty
• calculate an exact 50/40/10 Funding, Spot, and U-M Futures allocation and submit at most two sequential transfers through the current Binance page BAPI
• revalidate positions, orders, and balances before every transfer and report partial completion without retries or rollback
• document the private BAPI contract and add unit/source regression coverage

Validation

• npm test
• npm run build:binance-orderbook-trade
• npm run check:binance-orderbook-trade
• git diff --check

Live evidence

• current Binance transfer bundle builds { asset, amount, kindType } and calls /bapi/asset/v1/private/asset-service/wallet/transfer
• current bundle uses MAIN, CARD, and FUTURE private-BAPI account codes
• current bundle reads U-M transferable balance from /bapi/futures/v1/private/future/user-data/getMaxWithdrawAmount
• no authenticated transfer was executed during verification