Install COSS Calendar (@coss/calendar, react-day-picker) and add a co-located
DatePicker (Popover + Button trigger + Calendar) in patient-form-dialog. It
reads/writes the same formatted date string the form already uses (formatDate/
parseDate), so the Patient model is unchanged. Replace the free-text Visit 'Date'
and Problem 'Since' inputs with the picker.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>