Builds and broadcasts a user->external-address PSBT with change back to
the user's own address, fee deducted from the withdrawn amount, and
registers the confirmation handler that marks the withdrawal confirmed.
Shares the per-user lock with bets so a build never races a spend from
the same UTXO set.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
davideandClaude Sonnet 5
8380b80d12