[codex] Expose end-of-month scheduling on IborSwap

[gyx09212214-prog]

Summary

• expose the existing end_of_month schedule option on IborSwap
• pass the flag through to both fixed and floating swap legs
• add a regression test for the month-end 6M/1Y swap coupon grid case from Swap coupons grid issue #222

This keeps the existing default behavior unchanged while giving users a direct way to request EOM-aligned swap schedules when bootstrapping curves from month-end effective dates.

Closes #222.

Validation

• python -m pytest unit_tests\test_FinIborSwap.py -q
• git diff --check

[domokane]

Thanks. I agree this is a useful feature and exposing end_of_month on IborSwap seems consistent with the existing schedule machinery. Before merging, I’d like to check the hidden Unicode warning and possibly add one or two more tests around non-EOM effective dates and floating-leg schedules.