fix: 代码审查问题修复

- unit_of_work.py: 简化为纯 session 上下文管理器,消除 double-close 风险
- validation.py: 移除未使用的 import,简化 _score_to_1x2 逻辑
- repositories.py: 将 func 导入移到模块顶层
- 更新所有 get_uow() 调用点使用新接口(yield session 而非 uow 对象)

src/llm/eval.py

@@ -13,14 +13,13 @@ logger = logging.getLogger(__name__)
 
 async def settle_prediction(prediction_id: int, home_goals: int, away_goals: int) -> Prediction:
     """回填实际结果。"""
-    async with get_uow() as uow:
-        pred = await uow.session.get(Prediction, prediction_id)
+    async with get_uow() as session:
+        pred = await session.get(Prediction, prediction_id)
         if pred is None:
             raise ValueError(f"prediction {prediction_id} not found")
         pred.actual_home_goals = home_goals
         pred.actual_away_goals = away_goals
         pred.settled = True
-        await uow.commit()
         return pred
 
 
@@ -35,12 +34,12 @@ def _actual_1x2(home: int, away: int) -> str:
 
 async def get_eval_summary() -> dict:
     """按 provider × 模型聚合评估。"""
-    async with get_uow() as uow:
+    async with get_uow() as session:
         stmt = (
             select(Prediction)
             .where(Prediction.settled == True)
         )
-        result = await uow.session.execute(stmt)
+        result = await session.execute(stmt)
         rows = list(result.scalars().all())
 
         from collections import defaultdict