Fix asx-trading integration test fixture mismatch in factor_screen.py

Integration tests failing due to fixture mismatch in factor_screen.py. Signal_engine.py implements SMA crossover (Phase 1 design) not dividend-factor-based V2 engine. Need to align fixtures with actual implementation. Files: /opt/data/asx-trading/app/signal_engine.py, /opt/data/asx-trading/tests/factor_screen.py