New "fee_inclusive" field on funding wallet withdrawals

Broker API

Adds the optional fee_inclusive boolean to the funding wallet withdrawal request schema.

• When fee_inclusive is true, fees are deducted from usd_amount instead of being added on top, so the total debited from the account equals usd_amount exactly and the beneficiary receives usd_amount minus fees.
• The request is rejected when usd_amount is less than or equal to the fees.
• Defaults to false, which keeps the existing behavior of adding fees on top of usd_amount.

Affected Endpoints

• POST /v1beta/accounts/{account_id}/funding_wallet/withdrawal