feat: Realistic backtesting with OHLCV data (P5 continued)

Implemented realistic backtesting:
- Load real OHLCV close prices from intraday_pv.h5
- Calculate real price returns (pct_change)
- Apply signal positions to real returns with proper alignment
- Include spread costs (1.5 bps per trade)
- Fallback to factor proxy if OHLCV unavailable

Note: Sharpe values now realistic (~0 for random strategies).
Strategies need LLM to select predictive factors for positive Sharpe.

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

.gitignore

@@ -109,3 +109,7 @@ predix_quick_daytrading.py
 predix_smart_strategy_gen.py
 test/backtesting/test_smart_strategy_gen.py
 docs/SMART_STRATEGY_GEN.md
+
+# OpenACP local workspace (contains secrets)
+.openacp
+CLAUDE.md