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/AdminCampaignEdit.tsx

@@ -390,6 +390,9 @@ export default function AdminCampaignEdit() {
           <button
             type="button"
             onClick={() => setIsActive(!isActive)}
+            role="switch"
+            aria-checked={isActive}
+            aria-label={t('admin.campaigns.form.active')}
             className={`relative h-6 w-11 rounded-full transition-colors ${
               isActive ? 'bg-accent-500' : 'bg-dark-600'
             }`}