Let the coordinator trade with earned fees

[luckysori]

This is already possible when opening after settling. It is not possible when resizing. We want to remove this constraint for resizing, and remove a TODO for opening after settling.

This might make fee accounting a bit trickier, as the fees will be reinvested into trading and they might appear to be gone. That means we won't be able to rely on the size of the collateral reserve to calculate profits.

We will need to update the max_quantity function in the app.