fix(website): restore dotted hero backgrounds on PageHeader (#705)

* fix(website): restore radial hero backgrounds on page headers

PageHeader lost its decorative background when hero-bg was replaced by
DotField. Add a bottom-centered radial glow via a CSS class so it renders
reliably without Tailwind arbitrary-value parsing issues.

Also move the signup CTA gradient from an inline arbitrary Tailwind class
to the same CSS-class pattern for consistency.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix(website): restore dotted DotPattern hero background on PageHeader

Revert the radial glow added to page headers and bring back the static
DotPattern grid that was replaced by DotField in c31ad6395.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

apps/website/src/app.css

@@ -128,6 +128,15 @@ body {
   background: radial-gradient(circle at 50% 100%, rgba(2, 51, 189, 1) 1%, rgb(4, 2, 56) 100%);
 }
 
+.cio-cta-radial-bg {
+  background: radial-gradient(
+    circle at 50% 100%,
+    rgba(2, 51, 189, 0.92) 0%,
+    rgba(4, 15, 45, 0.98) 58%,
+    rgb(3, 7, 18) 100%
+  );
+}
+
 .embed {
   width: 100%;
   height: 315px;