server/internal/services/settings.go SaveSettings takes alerts and
email as required (non-pointer) values and writes them unconditionally
- absent fields would blank stored settings, not just leave them
alone. onLocalLoginChange was building its payload from the stale
loaded settings object instead of the in-progress form state
(thresholdMinutes/logRetentionDays) that handleSubmit uses, so editing
the offline threshold and then flipping the toggle silently reverted
the edit. Both paths now submit the same in-progress values.