Suggest the schedule stage and next-due date for a dose being administered — which dose of the series this is, and when the next one is due (generalizes the rabies 1-vs-3-year rule).

False when the type has no explicit schedule and isn't rabies — plain single-duration behavior.

True when prior doses exist but lapsed beyond the grace window, so the series restarts.

True when this dose is the last of a non-repeating schedule: nothing further is due, so there is no suggested interval, duration, or next-due date (and no reminders).

Server-computed next-due date from the given administration date (the FE default). Null when bool NextDoseSuggestionDto.IsSeriesComplete — nothing further is due.