fix(P0-01): missing score 不得变 0:0 — score_status + CHECK 约束

新增 matches.score_status(known/missing/unknown):
- 替换 ck_matches_finished_has_score 为 ck_matches_score_integrity:
  known → 必须有分; missing/unknown → goals 必须 NULL(不伪造 0:0)
- normalize: 完赛缺分不再静默降级为 scheduled,改设 score_status=missing
- events ingest: 创建/更新 Match 同步 score_status(比分由缺变 known / 确认缺分 missing)
- slices(form/h2h/home_away)/backtest: 显式加 score_status='known' 过滤完赛样本
- 迁移 0022 回填现有数据(绝不 UPDATE goals=0)

测试 tests/test_p0_score_status.py(9/9):约束存在性/Match 构造/normalize 行为。
54 相关测试全绿。

src/data/normalize.py

@@ -35,6 +35,8 @@ class NormalizedMatch:
     home_team: str
     away_team: str
     match_status: str = "finished"
+    # P0-01:比分可信度。known=可靠比分;missing=完赛缺分;unknown=待定。
+    score_status: str = "unknown"
     home_goals: int | None = None
     away_goals: int | None = None
     season_label: str = ""
@@ -217,5 +219,11 @@ def normalize_bzzoiro(raw: dict, league_type: str) -> NormalizedMatch | None:
     m.away_red_cards = _to_int(raw.get("away_red_cards", raw.get("red_cards_away")))
 
     if m.match_status == "finished" and m.home_goals is None:
-        m.match_status = "scheduled"
+        # P0-01: 完赛缺分不再静默降级为 scheduled(那会丢失「已完赛」事实);
+        # 保留 status=finished,score_status=missing,goals=NULL(禁止伪造 0:0)。
+        m.score_status = "missing"
+    elif m.home_goals is not None and m.away_goals is not None:
+        m.score_status = "known"
+    else:
+        m.score_status = "unknown"
     return m