complete i18n migration to /[locale]/ with EN+ES content

Full rewrite of the docs site under app/[locale]/ with next-intl
in localePrefix:"always" mode. Every page now exists at both
/en/<path> and /es/<path>; the root / shows a meta-refresh + JS
redirect to /<defaultLocale>/ so GitHub Pages serves something
on the apex URL.

Highlights:
- 107 doc pages migrated to file-per-page JSON namespaces under
  messages/en/ and messages/es/. Spanish content is fully
  translated (no copy-of-English placeholders).
- New documentation for the Active Suppressions section in the
  Settings tab and the per-event Dismiss dropdown in the Health
  Monitor modal.
- New screenshots: dismiss-duration-dropdown.png and an updated
  health-suppression-settings.png.
- Pagefind integrated for client-side search; index is built on
  every CI deploy (not committed).
- RSS feeds: per-locale at /<locale>/rss.xml plus root /rss.xml
  for backward compat.
- Removed the dead app/[locale]/guides/[slug]/ route — every
  guide now has its own static page and no markdown source
  remains.
- Fixed orphan link /guides/nvidia -> /guides/nvidia-manual in
  docs/hardware/nvidia-host.
- Removed obsolete components (footer2, calendar, drawer).

Verified locally with `npm ci && npm run build`: 2804 files in
out/, 231 pages indexed by pagefind, root redirect intact, both
locale roots and the new Active Suppressions docs render OK.

web/components/ui/screenshot-placeholder.tsx

@@ -0,0 +1,35 @@
+import React from "react"
+import { Camera } from "lucide-react"
+import { cn } from "@/lib/utils"
+
+interface ScreenshotPlaceholderProps {
+  description: string
+  filename?: string
+  className?: string
+}
+
+export const ScreenshotPlaceholder: React.FC<ScreenshotPlaceholderProps> = ({
+  description,
+  filename,
+  className,
+}) => {
+  return (
+    <div
+      className={cn(
+        "my-6 flex flex-col items-center justify-center rounded-lg border-2 border-dashed border-gray-300 bg-gray-50 p-8 text-center",
+        className,
+      )}
+      role="img"
+      aria-label={`Screenshot placeholder: ${description}`}
+    >
+      <Camera className="h-8 w-8 text-gray-400 mb-2" aria-hidden="true" />
+      <p className="text-sm font-medium text-gray-700 m-0">Screenshot needed</p>
+      <p className="text-sm text-gray-600 mt-1 max-w-md m-0">{description}</p>
+      {filename && (
+        <code className="mt-2 text-xs bg-white border border-gray-200 rounded px-2 py-0.5 text-gray-600">
+          {filename}
+        </code>
+      )}
+    </div>
+  )
+}