fix(a11y): switch semantics for admin form toggles

Add role=switch + aria-checked + aria-label to 12 ad-hoc toggle buttons across admin
create/edit forms (AdminCampaignCreate/Edit, AdminPromocodeCreate, AdminPromoGroupCreate,
AdminPromoOfferTemplateEdit, AdminPaymentMethodEdit, AdminTariffCreate) so screen readers
announce on/off state (WCAG 4.1.2).

src/pages/AdminPromoGroupCreate.tsx

@@ -378,6 +378,9 @@ export default function AdminPromoGroupCreate() {
           <button
             type="button"
             onClick={() => setApplyToAddons(!applyToAddons)}
+            role="switch"
+            aria-checked={applyToAddons}
+            aria-label={t('admin.promoGroups.form.applyToAddons')}
             className={`relative h-6 w-11 rounded-full transition-colors ${
               applyToAddons ? 'bg-accent-500' : 'bg-dark-600'
             }`}
@@ -396,6 +399,9 @@ export default function AdminPromoGroupCreate() {
           <button
             type="button"
             onClick={() => setIsDefault(!isDefault)}
+            role="switch"
+            aria-checked={isDefault}
+            aria-label={t('admin.promoGroups.form.isDefault')}
             className={`relative h-6 w-11 rounded-full transition-colors ${
               isDefault ? 'bg-accent-500' : 'bg-dark-600'
             }`}