fix: harden post-stop reentry lockdown

tests/unit/test_paper_trade_service.py

@@ -48,6 +48,74 @@ async def test_create_and_list_open(session):
     assert row["current_price"] == 110.0  # marked to the latest close
 
 
+async def test_create_trade_enforces_post_stop_lockdown_at_service_boundary(session):
+    blocked_id = await _seed(session, "LOCKQ", close=100.0)
+    released_id = await _seed(session, "FREEQ", close=100.0)
+    today = date.today()
+    market_sessions = [
+        today - timedelta(days=8),
+        today - timedelta(days=7),
+        today - timedelta(days=6),
+        today - timedelta(days=3),
+        today - timedelta(days=2),
+        today - timedelta(days=1),
+    ]
+    for market_date in market_sessions:
+        session.add(BenchmarkPrice(symbol="SPY", date=market_date, close=400.0))
+
+    def stopped_trade(ticker_id: int, closed_on: date) -> PaperTrade:
+        return PaperTrade(
+            user_id=1,
+            ticker_id=ticker_id,
+            direction="long",
+            entry_price=100.0,
+            shares=10.0,
+            stop_loss=95.0,
+            target=115.0,
+            status="closed",
+            opened_at=datetime.combine(
+                closed_on - timedelta(days=1), datetime.min.time(), tzinfo=timezone.utc
+            ),
+            close_price=95.0,
+            closed_at=datetime.combine(
+                closed_on, datetime.min.time(), tzinfo=timezone.utc
+            ),
+            close_reason="stop",
+        )
+
+    session.add_all(
+        [
+            stopped_trade(blocked_id, market_sessions[1]),
+            stopped_trade(released_id, market_sessions[0]),
+        ]
+    )
+    await session.commit()
+
+    with pytest.raises(ValidationError, match="1 market session remaining"):
+        await svc.create_trade(
+            session,
+            1,
+            symbol="LOCKQ",
+            direction="long",
+            entry_price=100.0,
+            shares=10.0,
+            stop_loss=95.0,
+            target=115.0,
+        )
+
+    trade = await svc.create_trade(
+        session,
+        1,
+        symbol="FREEQ",
+        direction="long",
+        entry_price=100.0,
+        shares=10.0,
+        stop_loss=95.0,
+        target=115.0,
+    )
+    assert trade.ticker_id == released_id
+
+
 async def test_close_uses_current_price(session):
     await _seed(session, "AAA", close=112.0)
     trade = await svc.create_trade(session, 1, symbol="AAA", direction="long",