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_log_service.py

@@ -123,6 +123,33 @@ def test_get_today_items_excludes_habits_not_scheduled_today(db_session, test_us
     assert quit_items == []
 
 
+# ---- get_yesterday_missed_items ----
+
+
+def test_get_yesterday_missed_items_includes_unchecked_scheduled_habit(db_session, test_user):
+    habit = _make_habit(db_session, test_user.id, name="어제 놓친 습관")
+
+    missed = log_service.get_yesterday_missed_items(db_session, test_user.id)
+    assert [item.habit_id for item in missed] == [habit.id]
+
+
+def test_get_yesterday_missed_items_excludes_already_checked(db_session, test_user):
+    habit = _make_habit(db_session, test_user.id)
+    _check(db_session, habit.id, date.today() - timedelta(days=1))
+
+    missed = log_service.get_yesterday_missed_items(db_session, test_user.id)
+    assert missed == []
+
+
+def test_get_yesterday_missed_items_excludes_habits_not_scheduled_yesterday(db_session, test_user):
+    yesterday = date.today() - timedelta(days=1)
+    other_day_mask = 1 << ((yesterday.weekday() + 1) % 7)  # 어제가 아닌 요일 하나만 선택
+    _make_habit(db_session, test_user.id, weekdays_mask=other_day_mask)
+
+    missed = log_service.get_yesterday_missed_items(db_session, test_user.id)
+    assert missed == []
+
+
 # ---- get_habit_stats: completion_rate ----