docs: verify against real WHP + capture real screenshots

Discovery against the demo account on whp01 surfaced several inaccuracies:

- Cache is Valkey (Redis wire-compatible), not Redis or Memcached.
  No Memcached is offered as a separate service.
- Site Monitoring is the sidebar label (not 'AI Monitor').
- 'Add a domain' has no Primary/Add-on distinction.
- Sites form: 'Container Type' (not 'Site type'), Number of Containers
  (1-10 for horizontal scaling), CPU per Container (default 0.25),
  Memory per Container (default 256MB), SSL inline on the same form.
- Backups: default retention 5 days / 10 backups; on-demand + scheduled;
  S3 backup targets are visible and configurable.
- Email: per-domain settings live behind 'Setup Instructions' on the
  Email page; mail server hostname is on the Dashboard (per-server,
  e.g. mail01.cloud-hosting.io), not per-domain.

Also reworked the screenshot pipeline:
- New shots.config.ts targets the real index.php?page=... URLs
- Added redactSensitive() step that runs before each screenshot to swap
  server names, IPs, mail hostnames, and demo-user-isms with neutral
  placeholders. This keeps docs portable across the fleet.
- Hides .brand-full and .navbar-text (top-bar server identifier and
  Welcome greeting).
- Captured 9 real WHP screenshots; removed stale placeholders.

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

@@ -16,7 +16,7 @@ Add-ons are **optional extras** you can layer onto your base hosting plan. Each
 
 ## What's available
 
-- **[Monitoring (AI Monitor)](/whp/add-ons/monitoring/)** — proactive alerts when something looks wrong (error spikes, brute-force attempts, exploit signatures).
+- **[Site Monitoring](/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.