fix: restore native date picker for birthday fields on iOS (#101)

Birthday date inputs in Settings (profile, new member, edit member) and
the Birthdays page were using type="text" with a custom mask, which
suppresses the native iOS date picker wheel. Switching to type="date"
with a plain ISO value restores the native picker while keeping the
existing parseDateInput / isDateInputValid logic intact.

Closes #98

Co-authored-by: Ulas Kalayci <ulas.kalayci@googlemail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

public/pages/birthdays.js

@@ -282,7 +282,7 @@ function openBirthdayModal({ mode, birthday = null }) {
         </div>
         <div class="form-group">
           <label class="form-label" for="bd-birth-date">${t('birthdays.birthDateLabel')}</label>
-          <input class="form-input js-date-input" id="bd-birth-date" type="text" value="${esc(formatDateInput(birthday?.birth_date))}" placeholder="${dateInputPlaceholder()}" inputmode="numeric">
+          <input class="form-input" id="bd-birth-date" type="date" value="${esc(birthday?.birth_date || '')}">
         </div>
         <div class="form-group">
           <label class="form-label" for="bd-photo">${t('birthdays.photoLabel')}</label>