Prefer external history before IBKR fallback

[Pigbibi]

Summary

• prefer the yfinance historical data path for strategy historical close/candle inputs
• keep IBKR historical data as fallback only when external history is empty or unavailable
• add tests that broker historical calls are skipped when fallback data exists and still used when fallback is empty

Why

IBKR historical requests are timing out for QQQ/BOXX in live prechecks. Waiting for two 60s broker timeouts per symbol can exceed the Cloud Run/Gunicorn request window. The strategies only need historical market context here, so the external data source should be the primary path for history.

Tests

• PYTHONPATH=. PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 /tmp/ues-test-venv/bin/python -m pytest -q tests/test_runtime_strategy_adapters.py
• ruff check application/runtime_strategy_adapters.py tests/test_runtime_strategy_adapters.py