docs(welfare): 15天不活跃清零金币/现金 设计文档(spec) (#144)

修改INACTIVITY_RESET_ENABLED语义，为false时清空金币操作只记录审计日志，不执行操作。

---------

Co-authored-by: guke <guke@autohome.com.cn>
Reviewed-on: #144

tests/test_inactivity_reset.py

@@ -302,11 +302,35 @@ def test_run_once_warns_then_resets() -> None:
         db.close()
 
 
-def test_worker_disabled_returns_none(monkeypatch) -> None:
+def test_worker_run_once_entry_dry_run(monkeypatch) -> None:
+    """ENABLED=false(默认语义)→ worker 常驻但只记审计不清(dry_run = not ENABLED)。"""
+    from sqlalchemy import select
+
     from app.core import inactivity_reset_worker as w
     from app.core.config import settings
-    monkeypatch.setattr(settings, "INACTIVITY_RESET_ENABLED", False)
-    assert w.start_inactivity_reset_worker() is None
+    from app.models.wallet import CoinAccount
+
+    monkeypatch.setattr(settings, "INACTIVITY_RESET_ENABLED", False)  # false = 只记审计
+    monkeypatch.setattr(settings, "INACTIVITY_RESET_DAYS", 15)
+    monkeypatch.setattr(settings, "INACTIVITY_WARN_DAYS_BEFORE", "")
+    monkeypatch.setattr(w, "_cn_today", lambda: date(2026, 2, 1))
+
+    db = SessionLocal()
+    try:
+        uid = _new_user(db, created_at=datetime(2026, 1, 1, tzinfo=timezone.utc), coin=100)
+        db.commit()
+    finally:
+        db.close()
+
+    w._run_once_entry()
+
+    db = SessionLocal()
+    try:
+        assert db.get(CoinAccount, uid).coin_balance == 100  # 没清
+        log = db.execute(select(InactivityResetLog).where(InactivityResetLog.user_id == uid)).scalar_one()
+        assert log.reason.endswith("dryrun")  # 记了审计
+    finally:
+        db.close()
 
 
 def test_worker_run_once_entry_executes(monkeypatch) -> None:
@@ -338,6 +362,44 @@ def test_worker_run_once_entry_executes(monkeypatch) -> None:
         db.close()
 
 
+def test_run_once_dry_run_records_audit_but_does_not_clear() -> None:
+    """dry-run:只写审计(标 dryrun)、不动钱、不预警;重复跑不重复记(streak dedup)。"""
+    from sqlalchemy import select
+
+    from app.integrations.notifier import LogNotifier
+    from app.models.wallet import CoinAccount, CoinTransaction
+    from app.repositories import inactivity
+
+    db = SessionLocal()
+    try:
+        today = date(2026, 2, 1)
+        old = _new_user(db, created_at=datetime(2026, 1, 10, tzinfo=timezone.utc), coin=100, cash=200, invite=300)
+        warn_uid = _new_user(db, created_at=datetime(2026, 1, 22, tzinfo=timezone.utc), coin=50)  # 预警窗
+        db.commit()
+
+        stats = inactivity.run_once(db, notifier=LogNotifier(), reset_days=15,
+                                    warn_stages=[7, 2], today=today, dry_run=True)
+        acc = db.get(CoinAccount, old)
+        assert (acc.coin_balance, acc.cash_balance_cents, acc.invite_cash_balance_cents) == (100, 200, 300)  # 原封
+        log = db.execute(select(InactivityResetLog).where(InactivityResetLog.user_id == old)).scalar_one()
+        assert log.coin_balance_before == 100 and log.reason.endswith("dryrun")   # 审计标 dryrun
+        assert db.execute(select(CoinTransaction).where(
+            CoinTransaction.user_id == old, CoinTransaction.biz_type == "inactivity_reset")).first() is None  # 无流水
+        assert stats["warned"] == 0                                              # dry-run 不预警
+        assert db.execute(select(InactivityNotificationLog).where(
+            InactivityNotificationLog.user_id == warn_uid)).first() is None
+        assert stats["cleared"] == 1                                             # dry-run:cleared=记了几条
+
+        # 再跑一次 → 不重复记(dedup),余额仍原封
+        inactivity.run_once(db, notifier=LogNotifier(), reset_days=15, warn_stages=[7, 2], today=today, dry_run=True)
+        assert len(db.execute(select(InactivityResetLog).where(
+            InactivityResetLog.user_id == old)).scalars().all()) == 1
+        assert db.get(CoinAccount, old).coin_balance == 100
+    finally:
+        db.rollback()
+        db.close()
+
+
 def test_admin_list_users_last_active_ignores_login() -> None:
     """admin 用户列表 last_active_at 改用共享口径:登录不算活跃(baseline=created_at)、只认活跃事件。"""
     from app.admin.repositories import queries