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/AdminPromocodeCreate.tsx

@@ -469,6 +469,9 @@ export default function AdminPromocodeCreate() {
             <button
               type="button"
               onClick={() => setIsActive(!isActive)}
+              role="switch"
+              aria-checked={isActive}
+              aria-label={t('admin.promocodes.form.active')}
               className={`relative h-6 w-10 rounded-full transition-colors ${
                 isActive ? 'bg-accent-500' : 'bg-dark-600'
               }`}
@@ -486,6 +489,9 @@ export default function AdminPromocodeCreate() {
             <button
               type="button"
               onClick={() => setFirstPurchaseOnly(!firstPurchaseOnly)}
+              role="switch"
+              aria-checked={firstPurchaseOnly}
+              aria-label={t('admin.promocodes.form.firstPurchaseOnly')}
               className={`relative h-6 w-10 rounded-full transition-colors ${
                 firstPurchaseOnly ? 'bg-accent-500' : 'bg-dark-600'
               }`}