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。

alembic/versions/0022_match_score_status.py

@@ -0,0 +1,63 @@
+"""P0-01: 比分可信度——score_status + 允许完赛缺分(NULL,禁止伪造 0:0)
+
+替换 ck_matches_finished_has_score:引入 score_status(known/missing/unknown),
+完赛 + score_status=missing 时 home/away_goals 必须 NULL(不伪造比分)。
+
+Revision ID: 0022_match_score_status
+Revises: 0021_match_source_event_id_unique
+Create Date: 2026-09-22
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = '0022_match_score_status'
+down_revision: Union[str, None] = '0021_match_source_event_id_unique'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # 1) 新增 score_status 列(默认 unknown)
+    op.add_column(
+        'matches',
+        sa.Column('score_status', sa.String(20), server_default='unknown', nullable=False),
+    )
+
+    # 2) 按现有数据回填 score_status(绝不写 goals=0):
+    #    - 有比分(两列均非 NULL) → known
+    #    - 无比分 + 完赛 → missing(缺分)
+    #    - 其余 → unknown
+    op.execute(
+        "UPDATE matches SET score_status = 'known'"
+        " WHERE home_goals IS NOT NULL AND away_goals IS NOT NULL"
+    )
+    op.execute(
+        "UPDATE matches SET score_status = 'missing'"
+        " WHERE match_status = 'finished' AND home_goals IS NULL AND away_goals IS NULL"
+    )
+
+    # 3) 删除旧约束,加新约束
+    op.drop_constraint('ck_matches_finished_has_score', 'matches', type_='check')
+    op.create_check_constraint(
+        'ck_matches_score_status_enum', 'matches',
+        "score_status IN ('known', 'missing', 'unknown')",
+    )
+    op.create_check_constraint(
+        'ck_matches_score_integrity', 'matches',
+        "match_status <> 'finished'"
+        " OR (score_status = 'known' AND home_goals IS NOT NULL AND away_goals IS NOT NULL)"
+        " OR (score_status IN ('missing', 'unknown') AND home_goals IS NULL AND away_goals IS NULL)",
+    )
+
+
+def downgrade() -> None:
+    op.drop_constraint('ck_matches_score_integrity', 'matches', type_='check')
+    op.drop_constraint('ck_matches_score_status_enum', 'matches', type_='check')
+    op.create_check_constraint(
+        'ck_matches_finished_has_score', 'matches',
+        "match_status <> 'finished' OR (home_goals IS NOT NULL AND away_goals IS NOT NULL)",
+    )
+    op.remove_column('matches', 'score_status')