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/pages/contact.vue

@@ -15,8 +15,8 @@ useHead({ title: () => `${copy.value.pages.contact.label} · dezky` })
 <template>
   <LandingPageHeader :label="c.label" :title="c.title" :intro="c.intro" />
 
-  <LandingContainer pad="56px 64px 160px">
-    <div :style="{ display: 'grid', gridTemplateColumns: 'repeat(2, minmax(0, 1fr))', gap: '24px', maxWidth: '760px' }">
+  <LandingContainer pad="clamp(56px, 8vw, 56px) clamp(20px, 5vw, 64px) clamp(80px, 12vw, 160px)">
+    <div :style="{ display: 'grid', gridTemplateColumns: 'repeat(auto-fit, minmax(min(100%, 320px), 1fr))', gap: '24px', maxWidth: '760px' }">
       <a
         :href="`mailto:${c.email}`"
         :style="{ display: 'block', padding: '28px', border: `1px solid ${t.border}`, borderRadius: '4px', background: t.surface }"