feat(factor): data_adapter BarData→AlphaLab polars 转换

实现 Task 4: 数据转换层

✅ 实现功能:
- convert_bars_to_alpha_df: BarData → polars DataFrame
- save_alpha_lab_data: 保存到 AlphaLab 格式

🔧 SPIKE 修正:
- 列名使用 open/high/low/close (非 open_price/close_price)
- 对齐 AlphaLab.save_bar_data 的 parquet 格式

📝 文件:
- sanguo_factor/data_adapter.py (核心实现)
- sanguo_factor/__init__.py (模块初始化)
- tests/factor/test_data_adapter.py (TDD 测试)
- tests/factor/conftest.py (测试配置)
- tests/factor/__init__.py (测试包)

⚠️  Environment Note:
- polars 依赖在 Python 3.14 环境安装困难
- 代码逻辑正确，待环境配置后验证测试

tests/factor/conftest.py

@@ -0,0 +1,8 @@
+"""Test configuration for factor module tests."""
+import sys
+import os
+
+# Add vnpy source to path
+_VNPY_SRC = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "vnpy_v4.4.0"))
+if _VNPY_SRC not in sys.path:
+    sys.path.insert(0, _VNPY_SRC)