add retroactive check for yesterday's missed habits on /today

Users often only realize a habit was missed the next day; a same-day-only
check made it impossible to record it after the fact.

tests/test_pages_today.py

@@ -1,4 +1,7 @@
+from datetime import date, timedelta
+
 from app.models.habit import ALL_WEEKDAYS_MASK, HabitType
+from app.models.habit_log import HabitLog
 from app.schemas.habit import HabitCreate
 from app.services import habit_service
 
@@ -38,3 +41,31 @@ def test_toggle_today_page_for_other_users_habit_returns_404(auth_client, db_ses
 
     response = auth_client.post(f"/today/{others_habit.id}/toggle")
     assert response.status_code == 404
+
+
+def test_today_page_shows_yesterday_missed_habit(auth_client, db_session, test_user):
+    _make_habit(db_session, test_user.id, name="어제 놓친 습관")
+
+    response = auth_client.get("/today")
+    assert response.status_code == 200
+    assert "어제 놓친 습관" in response.text
+
+
+def test_toggle_yesterday_page_creates_log_for_yesterday(auth_client, db_session, test_user):
+    habit = _make_habit(db_session, test_user.id, name="어제 습관")
+
+    response = auth_client.post(f"/today/{habit.id}/toggle-yesterday")
+    assert response.status_code == 200
+
+    yesterday = date.today() - timedelta(days=1)
+    log = db_session.query(HabitLog).filter_by(habit_id=habit.id, log_date=yesterday).one()
+    assert log is not None
+    # 체크되었으니 더 이상 "어제 놓친 습관" 목록에 나오지 않아야 한다.
+    assert "어제 놓친 습관" not in response.text
+
+
+def test_toggle_yesterday_page_for_other_users_habit_returns_404(auth_client, db_session, other_user):
+    others_habit = _make_habit(db_session, other_user.id, name="남의 습관")
+
+    response = auth_client.post(f"/today/{others_habit.id}/toggle-yesterday")
+    assert response.status_code == 404