feat(website): responsive / mobile layouts

Make the marketing site mobile-friendly across every page and section.
Desktop appearance is unchanged; all breakpoint logic targets <=768px.

- Fluid section padding via clamp(); equal grids use auto-fit/minmax,
  asymmetric grids stack to one column via scoped-CSS media queries
- Nav: real hamburger menu on mobile (links, lang toggle, login, CTA)
- ProductMockup: scales the whole dashboard to fit (zoom) instead of
  reflowing its internals into a tall stack
- Lower oversized heading clamp() minimums so titles no longer overflow
  at ~390px (hero, page headers, final CTA, brand cover/chapter)
- HowItWorks: row-gap when steps stack so node markers clear the text
- Compare + partners tables: stacked rows now label each value with its
  column (Dezky vs hyperscaler / CSP) instead of an ambiguous header
- Footer columns, tiers, calculator and tables stack cleanly on mobile

apps/website/components/landing/PageHeader.vue

@@ -11,7 +11,7 @@ const copy = useCopy()
 </script>
 
 <template>
-  <LandingContainer pad="120px 64px 0">
+  <LandingContainer pad="clamp(56px, 8vw, 120px) clamp(20px, 5vw, 64px) 0">
     <NuxtLink
       to="/"
       :style="{ fontFamily: '\'JetBrains Mono\', monospace', fontSize: '12px', color: t.fgMuted, letterSpacing: '0.04em', display: 'inline-flex', alignItems: 'center', gap: '8px' }"
@@ -24,7 +24,7 @@ const copy = useCopy()
 
     <h1 :style="{
       fontFamily: '\'Inter Tight\', \'Inter\', sans-serif', fontWeight: 600,
-      fontSize: 'clamp(40px, 5.4vw, 76px)', letterSpacing: '-0.035em', lineHeight: 1.0,
+      fontSize: 'clamp(30px, 5.4vw, 76px)', letterSpacing: '-0.035em', lineHeight: 1.0,
       margin: 0, textWrap: 'balance', color: t.fg, maxWidth: '900px',
     }">{{ title }}</h1>