docs(whp): add reference + 5 add-on articles, env.d.ts for font CSS imports

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

@@ -0,0 +1,39 @@
+---
+title: Add-ons overview
+description: Optional features you can layer on your hosting plan — monitoring, archival email, resource upgrades, and more.
+sidebar:
+  order: 1
+---
+
+import { Aside } from '@astrojs/starlight/components';
+import Support from '~/content/partials/support-link.mdx';
+
+Add-ons are **optional extras** you can layer onto your base hosting plan. Each is billed separately and can be enabled or removed from your client portal at any time.
+
+<Aside type="note">
+  An add-on is billed in addition to your base plan. Removing an add-on stops the charge from the next billing cycle.
+</Aside>
+
+## What's available
+
+- **[Monitoring (AI Monitor)](/whp/add-ons/monitoring/)** — proactive alerts when something looks wrong (error spikes, brute-force attempts, exploit signatures).
+- **[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.
+
+## How billing works
+
+Add-ons are **pro-rated** to align with your base plan's billing cycle and appear as separate line items on your next invoice. Cancelling an add-on stops it from the next cycle — you keep access through the end of the period you've already paid for.
+
+## How to enable an add-on
+
+1. Sign in to the [client portal](https://secure.anhonesthost.com/clientarea.php).
+2. Go to **Services → My Services** and pick your hosting plan.
+3. Click **Upgrade/Downgrade** (sometimes called **Add-ons** depending on the add-on).
+4. Pick the add-on, review the price, and confirm.
+
+WHP applies the change usually within a few minutes — no downtime for any of the add-ons listed here.
+
+## Still stuck?
+
+<Support />