fix(P0): 修复三处静默失效的阻断缺陷

P0-1 backtest 会话生命周期:
- _get_historical_matches 加 selectinload(league/home_team/away_team),
  并在 session 内物化为 BacktestCandidate 纯数据快照,避免 session
  关闭后访问惰性关系抛 MissingGreenlet
- except 收窄并改用 logger.exception 保留堆栈
- 移除未使用的 and_ / League 导入

P0-2 切片函数关系属性 MissingGreenlet:
- models.py 为 Match.league/home_team/away_team/stats 声明 lazy=selectin
- context_builder 的 _get_form/_get_h2h/_get_home_away 显式 selectinload
  (修复 form_slice/h2h_slice 恒定失败,被 fail-open 掩盖的问题)
- repositories.find_by_teams_and_date 加 selectinload(Match.stats)

P0-3 bzzoiro raw 变量泄漏导致血缘错乱:
- normalized_matches 改为携带 (nm, raw) 元组,内层循环解包
- source_event_id / source_record_id 现在取到正确 event id
- 已有比赛补建 stats 时补齐 source/source_event_id/retrieved_at/available_at
- 抽取 _match_key()/_to_date() 统一日期键构造 (P1-6)

src/data/bzzoiro.py

@@ -27,6 +27,26 @@ from src.db.models import League, Match, MatchStats, Team
 logger = logging.getLogger(__name__)
 
 
+def _to_date(value):
+    """把 datetime / date / str 统一成 `date`。"""
+    if value is None:
+        return None
+    if hasattr(value, "date") and callable(value.date):
+        return value.date()
+    return value
+
+
+def _match_key(home_team_id: int, away_team_id: int, match_date) -> tuple[int, int, str]:
+    """比赛去重键:(主队, 客队, 天级日期 ISO 字符串)。
+
+    统一在这里构造,避免"预加载时用 str(date)、写入时用 isoformat()"这类
+    隐式格式依赖 —— 两者当前恰好相等,但一旦有人改动其一就会静默失配,
+    导致所有比赛被判为不存在而重复插入。
+    """
+    d = _to_date(match_date)
+    return (home_team_id, away_team_id, d.isoformat() if d is not None else "")
+
+
 def _fetch_json_sync(path: str, params: dict | None = None, max_retries: int = 3) -> dict | list:
     """同步 HTTP(bzzoiro 客户端保持同步,在 async 函数里 run_in_executor)。"""
     base = settings.BZZOIRO_BASE.rstrip("/")
@@ -153,7 +173,9 @@ class BzzoiroSource:
             # === 批量优化: 预加载球队和已有比赛到内存 ===
             team_name_to_id: dict[str, int] = {}
             existing_matches: dict[tuple[int, int, str], Match] = {}  # 完整对象,避免重复查询
-            normalized_matches: list = []  # 缓存规范化结果,避免重复调用
+            # (NormalizedMatch, 原始 event) 成对保存:后续写 source_record_id 时
+            # 必须用配对的那条 event,不能依赖外层循环变量残留值。
+            normalized_matches: list[tuple] = []
 
             if raw_events:
                 # 一次遍历: 收集球队名 + 规范化
@@ -167,7 +189,7 @@ class BzzoiroSource:
                             logger.debug("normalize skip: %s", e)
                             league_r["errors"].append(f"normalize: {e}")
                             continue
-                        normalized_matches.append(nm)
+                        normalized_matches.append((nm, raw))
                         all_team_names.add(nm.home_team)
                         all_team_names.add(nm.away_team)
 
@@ -179,10 +201,10 @@ class BzzoiroSource:
                 # 预加载已有比赛(完整对象)
                 stmt = select(Match).where(Match.league_id == league.id)
                 for m in (await db.execute(stmt)).scalars():
-                    key = (m.home_team_id, m.away_team_id, str(m.match_date_date))
+                    key = _match_key(m.home_team_id, m.away_team_id, m.match_date_date)
                     existing_matches[key] = m
 
-            for nm in normalized_matches:
+            for nm, raw in normalized_matches:
                 # 球队: 内存查找 + 按需创建
                 home_team_id = team_name_to_id.get(nm.home_team)
                 if home_team_id is None:
@@ -201,8 +223,7 @@ class BzzoiroSource:
                     team_name_to_id[nm.away_team] = away_team_id
 
                 # 查找已有比赛: 内存查找
-                date_key = nm.date.date().isoformat() if hasattr(nm.date, "date") else str(nm.date)
-                match_key = (home_team_id, away_team_id, date_key)
+                match_key = _match_key(home_team_id, away_team_id, nm.date)
                 existing_match = existing_matches.get(match_key)
 
                 if existing_match is None:
@@ -212,7 +233,7 @@ class BzzoiroSource:
                         home_team_id=home_team_id,
                         away_team_id=away_team_id,
                         match_date=nm.date,
-                        match_date_date=nm.date.date() if hasattr(nm.date, "date") else nm.date,
+                        match_date_date=_to_date(nm.date),
                         match_status=nm.match_status,
                         home_goals=nm.home_goals,
                         away_goals=nm.away_goals,
@@ -263,7 +284,14 @@ class BzzoiroSource:
                         existing_match.match_stage = nm.match_stage
                         changed = True
                     if existing_match.stats is None and (nm.home_xg is not None or nm.away_xg is not None):
-                        existing_match.stats = MatchStats(match_id=existing_match.id)
+                        now = datetime.now(timezone.utc)
+                        existing_match.stats = MatchStats(
+                            match_id=existing_match.id,
+                            source="bzzoiro",
+                            source_event_id=str(raw.get("id", "")),
+                            retrieved_at=now,
+                            available_at=now,
+                        )
                         db.add(existing_match.stats)
                         await db.flush()
                     if existing_match.stats is not None: