feat(app): add prerender, self-hosted fonts and privacy page

Fonts come from npm, not Google, so no third-party font requests.
Pages are prerendered at build time; browser-only code is guarded.
nginx serves per-route HTML, a real 404 and gzip.

src/tailwind.css

@@ -44,16 +44,6 @@
   @apply inline-block w-[15px] h-[15px] border border-gray-300 align-middle mr-[5px];
 }
 
-/*
-  Preflight is off, so a bare <button> keeps the UA font (13.33px Arial) instead of
-  the page font. Anything that should read as a link but has to stay a button for
-  accessibility uses this.
-*/
-@utility link-button {
-  font: inherit;
-  @apply text-link font-medium bg-transparent p-0 cursor-pointer hover:text-link-hover hover:underline;
-}
-
 @utility card-gradient-bar {
   @apply relative;