fix(quickadapter): bound take-profit stage to filled take-profit exits

fix(quickadapter): bound take-profit stage to filled take-profit exits

Derive the take-profit stage from filled take-profit-tagged exit orders
clamped to the final full-exit stage, instead of nr_of_successful_exits
plus in-flight exit orders. This stops the stage index from overshooting
its maximum (e.g. take_profit_*_4 while the final stage is 3) when a
final exit order is in flight or a non-take-profit exit fills.

Guard custom_exit against re-issuing the final take-profit exit while an
order is open by returning None after the model-expiry and reversal
safety exits and before the take-profit stage computation, so safety
exits still fire while in-flight orders no longer trigger a duplicate
take-profit exit.