refactor: 代码审查修复 - 日期过滤、性能优化、数据泄露防护

- 修复 data_loader.py 财务数据日期过滤，支持按范围加载
- 优化 MADClipper 使用窗口函数替代 join，提升性能
- 修复训练日期边界问题，添加1天间隔避免数据泄露
- 新增 .gitignore 规则忽略训练输出目录

src/data/api_wrappers/__init__.py

@@ -20,6 +20,7 @@ Example:
 """
 
 from src.data.api_wrappers.api_daily import get_daily, sync_daily, preview_daily_sync, DailySync
+from src.data.api_wrappers.financial_data.api_income import get_income, sync_income, IncomeSync
 from src.data.api_wrappers.api_bak_basic import get_bak_basic, sync_bak_basic
 from src.data.api_wrappers.api_namechange import get_namechange, sync_namechange
 from src.data.api_wrappers.api_stock_basic import get_stock_basic, sync_all_stocks
@@ -37,6 +38,10 @@ __all__ = [
     "sync_daily",
     "preview_daily_sync",
     "DailySync",
+    # Income statement
+    "get_income",
+    "sync_income",
+    "IncomeSync",
     # Historical stock list
     "get_bak_basic",
     "sync_bak_basic",