feat: add gift subscription toggle to admin branding settings

Add CABINET_GIFT_ENABLED toggle in Admin Settings > Branding > Interface Options,
alongside existing fullscreen and email auth toggles. Includes updateGiftEnabled
API method and i18n keys for all 4 locales (ru/en/zh/fa).

src/components/admin/BrandingTab.tsx

@@ -35,6 +35,11 @@ export function BrandingTab({ accentColor = '#3b82f6' }: BrandingTabProps) {
     queryFn: brandingApi.getEmailAuthEnabled,
   });
 
+  const { data: giftSettings } = useQuery({
+    queryKey: ['gift-enabled'],
+    queryFn: brandingApi.getGiftEnabled,
+  });
+
   // Mutations
   const updateBrandingMutation = useMutation({
     mutationFn: brandingApi.updateName,
@@ -76,6 +81,13 @@ export function BrandingTab({ accentColor = '#3b82f6' }: BrandingTabProps) {
     },
   });
 
+  const updateGiftMutation = useMutation({
+    mutationFn: (enabled: boolean) => brandingApi.updateGiftEnabled(enabled),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['gift-enabled'] });
+    },
+  });
+
   const handleLogoUpload = (e: React.ChangeEvent<HTMLInputElement>) => {
     const file = e.target.files?.[0];
     if (file) {
@@ -225,6 +237,18 @@ export function BrandingTab({ accentColor = '#3b82f6' }: BrandingTabProps) {
               disabled={updateEmailAuthMutation.isPending}
             />
           </div>
+
+          <div className="flex items-center justify-between rounded-xl bg-dark-700/30 p-4">
+            <div>
+              <span className="font-medium text-dark-100">{t('admin.settings.giftEnabled')}</span>
+              <p className="text-sm text-dark-400">{t('admin.settings.giftEnabledDesc')}</p>
+            </div>
+            <Toggle
+              checked={giftSettings?.enabled ?? false}
+              onChange={() => updateGiftMutation.mutate(!(giftSettings?.enabled ?? false))}
+              disabled={updateGiftMutation.isPending}
+            />
+          </div>
         </div>
       </div>
     </div>