polish: consolidate typography to next/font variables, add atelier utility classes

- Remove Google Fonts @import from 4 components (SiteHeader, LandingPageWrapper,
  TestimonialsAndCTA, FeaturesAndStats) — eliminate render-blocking external
  request and font flash
- Replace all unloaded Cormorant Garamond / Playfair Display / DM Sans /
  Plus Jakarta Sans references with the existing next/font variables
  (Fraunces, Manrope, Fragment_Mono) — visual coherence with the design system
- Update 9 pages (blog, brands, changelog, maintenance, protected-example,
  roadmap, security, waitlist, WaitlistForm) to use the loaded Fraunces
- Fix dead --font-geist / --font-jetbrains-mono references in
  admin-design-system.css (now point to --font-manrope / --font-fragment-mono
  which are actually loaded)
- Add atelier-pill, atelier-numerals, atelier-fineprint, atelier-canvas-soft
  utility classes; .atelier-input:focus-visible refined ring
- Add .ha-field-textarea, .ha-scroll, .ha-skeleton to admin design system
- Extend prefers-reduced-motion guard to atelier-enter/stagger/shimmer
- Apply atelier-fineprint to login/not-found/error pages for consistency
- No structural changes; build passes, 0 type errors

src/app/brands/page.tsx

@@ -224,7 +224,7 @@ export default function BrandsPage() {
 
       <style jsx>{`
         .brands-page {
-          font-family: 'Plus Jakarta Sans', system-ui, sans-serif;
+          font-family: var(--font-manrope);
           background: #ffffff;
           min-height: 100vh;
         }