Fix broken factor_screen.py pytest tests (8 failures)

asx-trading test suite has 8 failures in factor_screen.py due to fixture mismatch. Fix fixtures so tests pass. Signal engine currently uses SMA crossover instead of dividend-factor V2 from design — check if this is intentional or a regression.\n\nAcceptance: pytest run shows 0 failures for factor_screen tests.\n\nFiles: /opt/data/asx-trading/ (test directory + factor_screen.py)\n\nTags: asx-trading, testing

Note (2026-06-28T16:41:33Z)

Picked up by autopilot at 2026-06-28T10:30. Plan: locate factor_screen.py and its test files, run the failing tests to see errors, then fix the root cause of all 8 failures in one pass.