docs(whp): add backend-switching how-to + Optimized Webserver (OLS) add-on page

- how-to/switching-site-backend: change a site's container type between standard
  PHP/FPM and the premium LiteSpeed/OLS backend; required steps to move off
  premium before cancelling the add-on (panel blocks the disable otherwise).
- add-ons/optimized-webserver: what the OLS/LSCache add-on is, advantages, when
  NOT to use it, how to enable/use, and cancellation requirements.
- add-ons/overview: list the new add-on.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/content/docs/whp/add-ons/optimized-webserver.mdx

@@ -0,0 +1,92 @@
+---
+title: Optimized Webserver (OpenLiteSpeed + LSCache)
+description: Run your sites on OpenLiteSpeed with server-level full-page caching for dramatically faster page delivery — ideal for WordPress and other dynamic CMS sites.
+sidebar:
+  order: 5
+---
+
+import { Aside } from '@astrojs/starlight/components';
+import PaidAddon from '~/content/partials/paid-addon-callout.mdx';
+import Support from '~/content/partials/support-link.mdx';
+
+<PaidAddon />
+
+The Optimized Webserver add-on moves your sites from standard Apache/PHP onto our shared **OpenLiteSpeed** pool with the **LiteSpeed Cache (LSCache)** engine. LSCache is a server-level full-page cache built directly into the web server — cached pages are served in a few milliseconds, before PHP ever runs.
+
+This is an **account-level** add-on: purchase it once and you can put as many of your hosted sites on the premium backend as you like — no per-site charge.
+
+## Why use it
+
+### Dramatically faster cacheable pages
+
+LSCache operates at the web-server layer, not inside WordPress or PHP. When a page is cached, the response is served in a few milliseconds with no PHP execution and no database queries. For a WordPress site that normally takes 300–800 ms to generate a page, cached hits feel instant to visitors.
+
+### Built for dynamic CMS sites — especially WordPress
+
+OpenLiteSpeed works directly with the official [LiteSpeed Cache plugin for WordPress](https://wordpress.org/plugins/litespeed-cache/). The plugin manages cache purging automatically: publish a post, update a page, or complete a WooCommerce order and the right cache entries are dropped so visitors see fresh content immediately.
+
+### Handles traffic spikes efficiently
+
+Because cached hits skip PHP and the database entirely, the server can absorb a burst of traffic without proportionally increasing CPU or memory load. Sites on the standard backend can stall under sudden spikes; on LSCache, most of that load is absorbed before it reaches PHP.
+
+### HTTP/3 and QUIC
+
+OpenLiteSpeed has native HTTP/3/QUIC support. Visitors on modern browsers get the lower-latency transport automatically — no configuration needed.
+
+### Efficient memory profile on shared hosting
+
+Our shared OpenLiteSpeed pool is tuned for multi-tenant use. You get the performance benefits without needing a dedicated server or a much larger container allocation.
+
+## When you may NOT want it
+
+<Aside type="caution">
+  Read this section before switching. The performance gains are real, but not every site benefits equally — and there are a few cases where the standard backend is the right choice.
+</Aside>
+
+- **Purely static sites or very low-traffic sites.** If your site serves a handful of visitors a day, the standard backend is already fast enough. You won't see a meaningful difference, and the add-on cost won't pay off.
+- **Highly personalised or uncacheable output.** Sites that generate unique content per visitor on every request (custom dashboards, paywalled pages with per-user state, complex session-driven flows) can't benefit much from a full-page cache. LSCache has smarts for partial caching, but if the majority of your pages can't be cached, the speed gains are limited.
+- **You haven't tested your site on it.** We don't auto-migrate sites. You opt each site in yourself, verify everything looks right — plugins, checkout flows, member areas — and only then commit. Cache behaviour can surface edge cases (stale content after a post update, logged-in users seeing cached guest pages) that need a plugin configuration tweak. Test before you rely on it.
+- **Cold cache after switching.** The first time each page is requested after you switch, it runs through PHP as normal (the cache starts empty). Subsequent hits are served from cache. Don't judge performance on the very first load.
+- **Don't stack full-page cache plugins.** If you already run a second full-page caching plugin (W3 Total Cache, WP Super Cache, WP Fastest Cache, etc.) alongside LSCache, they'll conflict. Disable any other full-page caching plugin when you switch; LSCache replaces it, not supplements it. Object-cache and CDN integrations are fine.
+
+## How to enable it
+
+### Step 1 — Purchase the add-on
+
+The Optimized Webserver add-on is purchased from the [client portal](https://secure.anhonesthost.com/clientarea.php). Go to **Services → My Services**, open your hosting plan, then **Upgrade/Downgrade → Optimized Webserver**. Once confirmed, the option becomes available in WHP within a few minutes.
+
+### Step 2 — Switch individual sites onto it
+
+Enabling the add-on at the account level doesn't automatically move any of your sites. You opt each site in one at a time:
+
+1. In WHP, go to **Sites** and click **Edit** on the site you want to switch.
+2. Under **PHP / Backend**, choose one of the **LiteSpeed PHP** options.
+3. Save. The site container is recreated on the OpenLiteSpeed pool — there is a brief moment of downtime (usually under 30 seconds) during the switchover.
+
+For a full walkthrough, see [Switching a site's backend](/whp/how-to/switching-site-backend/).
+
+### Step 3 — Install (or verify) the LiteSpeed Cache plugin
+
+For WordPress sites, install the free [LiteSpeed Cache plugin](https://wordpress.org/plugins/litespeed-cache/) from the WordPress plugin directory if it isn't already active. It handles cache purging on content changes automatically. Default settings work well for most sites; advanced tuning options are in the plugin's settings panel.
+
+<Aside type="note">
+  If you were previously running another full-page caching plugin, deactivate (don't just disable caching — actually deactivate) it after switching. Leaving two full-page caches active causes unpredictable behaviour.
+</Aside>
+
+## Cancelling
+
+To cancel the Optimized Webserver add-on you must first **move all your sites back to a standard backend**. The panel will block cancellation while any site is still using a LiteSpeed PHP option.
+
+Switch each affected site back via **Sites → Edit → PHP / Backend**, then cancel the add-on from the [client portal](https://secure.anhonesthost.com/clientarea.php).
+
+For the site-switching steps, see [Switching a site's backend](/whp/how-to/switching-site-backend/).
+
+## Related
+
+- [Add-ons overview](/whp/add-ons/overview/)
+- [Resource upgrades](/whp/add-ons/resource-upgrades/) — if you need more CPU or RAM rather than a faster cache layer.
+- [Site Monitoring](/whp/add-ons/monitoring/) — pair with Optimized Webserver to catch any cache-related issues early.
+
+## Still stuck?
+
+<Support />

src/content/docs/whp/add-ons/overview.mdx

@@ -20,6 +20,7 @@ Add-ons are **optional extras** you can layer onto your base hosting plan. Each
 - **[Archival email](/whp/add-ons/archival-email/)** — long-term, searchable retention of your mail outside the live mailbox.
 - **[Resource upgrades](/whp/add-ons/resource-upgrades/)** — extra CPU, RAM, or storage without changing plans.
 - **[Email upgrades](/whp/add-ons/email-upgrades/)** — extra mailboxes or larger per-mailbox storage caps.
+- **[Optimized Webserver](/whp/add-ons/optimized-webserver/)** — run your sites on OpenLiteSpeed with server-level LSCache for dramatically faster page delivery.
 
 ## How billing works
 

src/content/docs/whp/how-to/switching-site-backend.mdx

@@ -0,0 +1,100 @@
+---
+title: Switching your site's backend
+description: Change the web engine (container type) running a site — standard PHP/FPM or the premium LiteSpeed/OpenLiteSpeed tier.
+sidebar:
+  order: 5
+---
+
+import { Steps, Aside } from '@astrojs/starlight/components';
+import SignIn from '~/content/partials/signing-in.mdx';
+import Support from '~/content/partials/support-link.mdx';
+
+Every WHP site runs inside a container. The **container type** determines the web engine that serves your site's files and runs your PHP code. Most sites use a standard PHP or PHP-FPM container, which handles the vast majority of WordPress and PHP workloads well. If you've enabled the **Optimized Webserver** add-on, you also have access to LiteSpeed/OpenLiteSpeed (OLS) container types — a premium engine known for its built-in full-page cache (LSCache) and lower memory usage under traffic.
+
+Switching backends is a one-step change in the Sites editor, but it does briefly restart your container, so plan for a few seconds of downtime.
+
+## Before you start
+
+- You need **admin access** to your WHP account.
+- If you want to switch **onto** a LiteSpeed backend, your account must have the [Optimized Webserver add-on](/whp/add-ons/optimized-webserver/) enabled. If it isn't, those container types won't appear in the dropdown.
+- About 2 minutes, plus a brief site restart.
+
+## Sign in to WHP
+
+<SignIn />
+
+## Steps
+
+<Steps>
+
+1. In the sidebar, click **Sites**.
+
+2. Find the site you want to change and click **Edit** (the pencil icon next to it).
+
+3. In the **Edit Site** form, locate the **Container Type** (or **PHP Version / Backend**) dropdown.
+
+4. Select the backend you want:
+   - **PHP** or **PHP-FPM** options — standard shared webserver tier, suitable for most WordPress and PHP sites.
+   - **LiteSpeed PHP** options (e.g. *LiteSpeed PHP 8.x*) — premium OLS tier. These only appear if the Optimized Webserver add-on is active on your account.
+
+5. Click **Save**. WHP recreates the container with the new engine. Expect a brief moment of downtime (typically a few seconds) while the container restarts.
+
+</Steps>
+
+<Aside type="note">
+  After switching backends, any server-side page cache starts cold. For LiteSpeed sites this means LSCache has nothing cached yet — your first few page loads will be slightly slower while the cache warms up. This is normal and resolves on its own within minutes.
+</Aside>
+
+## Switching onto the premium LiteSpeed backend
+
+The LiteSpeed/OpenLiteSpeed container types are part of the **Optimized Webserver** add-on. If you open the Container Type dropdown and don't see any LiteSpeed options, the add-on isn't enabled on your account yet.
+
+To enable it:
+
+1. Visit the [Optimized Webserver add-on page](/whp/add-ons/optimized-webserver/) for details and pricing.
+2. Enable it from your [client portal](https://secure.anhonesthost.com/clientarea.php).
+3. Once active, the LiteSpeed PHP options will appear in the Container Type dropdown when editing any site.
+
+## Before cancelling the Optimized Webserver add-on
+
+<Aside type="caution">
+  You must move **all** of your sites off the LiteSpeed backend before you can cancel or disable the Optimized Webserver add-on. The system will block the cancellation and show an error listing every site that still needs to be moved.
+</Aside>
+
+To prepare for cancellation, switch each affected site back to a standard PHP or PHP-FPM container type:
+
+<Steps>
+
+1. In the sidebar, click **Sites**.
+
+2. For each site currently on a LiteSpeed container type, click **Edit**.
+
+3. Change the **Container Type** to a standard **PHP** or **PHP-FPM** option.
+
+4. Click **Save** and wait for the container to restart before moving to the next site.
+
+5. Repeat until no sites are on a LiteSpeed backend.
+
+</Steps>
+
+Once all sites are on standard backends, you can cancel or disable the add-on from your [client portal](https://secure.anhonesthost.com/clientarea.php) without errors.
+
+## Troubleshooting
+
+**LiteSpeed options don't appear in the dropdown.** The Optimized Webserver add-on is not enabled on your account. See [Optimized Webserver](/whp/add-ons/optimized-webserver/) to add it.
+
+**Site doesn't come back up after switching.** Wait 30 seconds and reload — the container may still be starting. If the site is still down after a minute, contact support.
+
+**Cancelling the add-on shows an error listing sites.** Switch each listed site to a standard PHP/PHP-FPM backend first (see the steps above), then retry the cancellation.
+
+**LiteSpeed cache not serving cached pages after the switch.** This is expected — the cache starts empty after every container recreation. It warms up automatically as visitors load pages.
+
+## Related
+
+- [Create a site](/whp/how-to/create-a-site/)
+- [Optimized Webserver add-on](/whp/add-ons/optimized-webserver/)
+- [Resource upgrades](/whp/add-ons/resource-upgrades/)
+
+## Still stuck?
+
+<Support />