fix(status): status page fails to fetch uptime data for every window

## Problem
`status.worldmonitor.app` renders (UptimeRobot) but displays
"There was an error while fetching the data." No uptime figures load for any
window — 24h, 7d, 30d, 90d all fail.

## Why it matters
A broken status page during vendor diligence is strictly worse than not having
one. It is the page a buyer visits specifically to answer "is this reliable?",
and it currently answers "no" for the wrong reason.

## Fix
Diagnose the UptimeRobot embed (likely an expired/rotated API key, a deleted
monitor, or a changed public-status-page slug). Verify all four windows render.

While in there: we have no SLA anywhere on the site, which is a separate blocker
for the embed motion — see the `chore(trust)` issue.

## Acceptance
- [ ] All four windows render real figures
- [ ] A synthetic check alerts if the status page itself errors
- [ ] Linked from the docs and the eventual /security page

Effort: S (~0.5d).

Start by inspecting the status.worldmonitor.app UptimeRobot embed and its current monitor or public-status-page configuration. Verify that 24h, 7d, 30d, and 90d windows render real figures, add a synthetic check for status-page errors, and link the page from the docs and eventual /security page.

Written by the indexing model from the issue text.