fix: keep closed week snapshot in sync when days change

When a day is closed, re-closed, or reopened, DayService now
recomputes worked_ms and delta_ms on the closed week containing
that day (if the week is already closed). This prevents stale
delta values after editing entries and re-closing a day.

- DayService.recomputeWeek: sums worked_ms from all closed_days
  in the week, updates closed_weeks row preserving expected_ms
- NewDayService now takes ClosedWeekStore
- WeekKeyForDayKey exported helper (used by DayService)
- TestWeekSnapshotUpdatesWhenDayReopened regression test

internal/service/entry_service_test.go

@@ -208,10 +208,11 @@ func TestUpdateRejectsClosedDay(t *testing.T) {
 
 	entryStore := store.NewEntryStore(db)
 	closedDayStore := store.NewClosedDayStore(db)
+	closedWeekStore := store.NewClosedWeekStore(db)
 	settingsStore := store.NewSettingsStore(db)
 	tz, _ := time.LoadLocation("UTC")
 	svc := service.NewEntryService(entryStore, closedDayStore, settingsStore, tz)
-	daySvc := service.NewDayService(entryStore, closedDayStore, settingsStore, tz)
+	daySvc := service.NewDayService(entryStore, closedDayStore, closedWeekStore, settingsStore, tz)
 
 	entry, _ := svc.Start(ctx, "")
 	svc.Stop(ctx)