Fix broken tests in ASX trading platform

19 failed + 16 errors. Main issues: (1) test_dividend_layer.py - KeyError/assertion failures; (2) test_ibkr_connection.py - ibapi module missing; (3) test_runner.py - TypeError and SimulationConfig failures. Need to fix each category.

Note (2026-06-28T17:40:04Z)

Picked up by ralph at 2026-06-28T16:50 BNE. Plan: Fix test_dividend_layer.py first (largest failure group), then test_runner.py, then skip IBKR connection tests (blocked on ibapi module).