Fee calculation uses faceValue instead of amountToTransfer

Nobody has claimed this yet.

## Problem

In `ticketBroker.ts`, the `WinningTicketRedeemed` handler uses `event.params.faceValue` for fee distribution math. However, the contract's `updateTranscoderWithFees` receives `amountToTransfer`, which can be **less** than `faceValue` when the sender's deposit is insufficient.

### Contract flow (MixinTicketBrokerCore.sol:137-155)

```solidity
if (_ticket.faceValue > sender.deposit) {
amountToTransfer = sender.deposit.add(
claimFromReserve(_ticket.sender, _ticket.recipient, _ticket.faceValue.sub(sender.deposit))
);
sender.deposit = 0;
} else {
amountToTransfer = _ticket.faceValue;
}

winningTicketTransfer(_ticket.recipient, amountToTransfer, _ticket.auxData);
```

`winningTicketTransfer` → `updateTranscoderWithFees(_recipient, _amount, ...)` uses `amountToTransfer`.

But the `WinningTicketRedeemed` event emits `faceValue`, not `amountToTransfer`:
```solidity
emit WinningTicketRedeemed(_ticket.sender, _ticket.recipient, _ticket.faceValue, ...);
```

### Impact

When a sender is underfunded (`deposit < faceValue`), the subgraph overcounts:
- `delegatorsFees` and `transcoderCommissionFees` are computed on a higher base
- `cumulativeFeeFactor` update is slightly inflated
- `pendingFeeCommission` / `lifetimeFeeCommission` are slightly inflated

In the normal case (`deposit >= faceValue`), the values are equal and there is no issue.

### Possible fix

The `WinningTicketTransfer` event emits `amountToTransfer` — could use that instead of or in addition to `WinningTicketRedeemed.faceValue` for the fee math.

Start in ticketBroker.ts and trace the WinningTicketRedeemed handler's fee calculations alongside the WinningTicketTransfer flow in MixinTicketBrokerCore.sol:137-155. Verify the indexed fee values for an underfunded sender against amountToTransfer, then run the subgraph's relevant indexing or test checks; done means the fee fields no longer use the larger faceValue base in that case.

Written by the indexing model from the issue text.