- Backend: /due endpoint now matches both NULL and empty string for
recurrence_rule (form was sending '' not null, excluding all reminders)
- Form: sends null instead of '' for empty recurrence_rule
- ReminderForm: replaced datetime-local with date + hour/minute/AM-PM
selects for 12-hour time format
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>