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/predict.py

@@ -145,10 +145,9 @@ async def _predict_single(
         raise RuntimeError(f"LLM 输出校验失败: {e}")
 
     # 4. 存预测(使用 UnitOfWork 统一事务)
-    async with get_uow() as uow:
-        db = uow.session
+    async with get_uow() as session:
         # 验证 match 存在
-        m = await db.get(Match, match_id)
+        m = await session.get(Match, match_id)
         if m is None:
             raise ValueError(f"match {match_id} not found")
 
@@ -169,9 +168,8 @@ async def _predict_single(
             cutoff_at=cutoff_at,
             input_hash=input_hash,
         )
-        db.add(pred)
-        await db.commit()
-        await db.refresh(pred)
+        session.add(pred)
+        await session.refresh(pred)
 
         result = PredictResult(
             prediction_id=pred.id,
@@ -190,5 +188,4 @@ async def _predict_single(
 
         # 5. 写入缓存
         _set_cached(match_id, settings.LLM_PROVIDER, provider.model, version, result)
-        await uow.commit()
         return result