fix(pre-alpha): preserve injected backtest services

tests/helpers_backtest_sources.py

@@ -0,0 +1,10 @@
+from __future__ import annotations
+
+from datetime import date
+
+from app.services.backtesting.historical_provider import DailyClosePoint
+
+
+class StaticBacktestSource:
+    def load_daily_closes(self, symbol: str, start_date: date, end_date: date) -> list[DailyClosePoint]:
+        return [DailyClosePoint(date=date(2024, 1, 3), close=123.0)]