refactor(factor): 完全重构因子计算框架 - 引入DSL表达式系统

- 删除旧因子框架：移除 base.py、composite.py、data_loader.py、data_spec.py
  及所有子模块（momentum、financial、quality、sentiment等）
- 新增DSL表达式系统：实现 factor DSL 编译器和翻译器
  - dsl.py: 领域特定语言定义
  - compiler.py: AST编译与优化
  - translator.py: Polars表达式翻译
  - api.py: 统一API接口
- 新增数据路由层：data_router.py 实现字段到表的动态路由
- 新增API封装：api_pro_bar.py 提供pro_bar数据接口
- 更新执行引擎：engine.py 适配新的DSL架构
- 重构测试体系：删除旧测试，新增 test_dsl_promotion.py、
  test_factor_integration.py、test_pro_bar.py
- 清理文档：删除8个过时文档（factor_design、db_sync_guide等）

src/data/api_wrappers/api_trade_cal.py

@@ -8,7 +8,7 @@ import pandas as pd
 from typing import Optional, Literal
 from pathlib import Path
 from src.data.client import TushareClient
-from src.data.config import get_config
+from src.config.settings import get_settings
 
 # Module-level flag to track if cache has been synced in this session
 _cache_synced = False
@@ -18,7 +18,7 @@ _cache_synced = False
 # Trading calendar cache file path
 def _get_cache_path() -> Path:
     """Get the cache file path for trade calendar."""
-    cfg = get_config()
+    cfg = get_settings()
     return cfg.data_path_resolved / "trade_cal.h5"
 
 
@@ -296,8 +296,8 @@ def get_first_trading_day(
     trading_days = get_trading_days(start_date, end_date, exchange)
     if not trading_days:
         return None
-    # Trading days are sorted in descending order (newest first) from cache
-    return trading_days[-1]
+    # Return the earliest trading day
+    return min(trading_days)
 
 
 def get_last_trading_day(
@@ -318,8 +318,8 @@ def get_last_trading_day(
     trading_days = get_trading_days(start_date, end_date, exchange)
     if not trading_days:
         return None
-    # Trading days are sorted in descending order (newest first) from cache
-    return trading_days[0]
+    # Return the latest trading day
+    return max(trading_days)
 
 
 if __name__ == "__main__":