feat(website): footer sub-pages + shared page layout

Wire every footer link to a real route. Adds a shared `page` layout (Nav +
content + Footer), reusable PageHeader/ComingSoon components, six content pages
(about, contact, brand, roadmap, changelog, migration), and a dynamic [slug]
catch-all for the not-yet-built pages — unknown slugs 404, legal slugs get a
distinct "contact us" body.

Footer links repointed from dead "#" to real paths; section anchors ("/#suite")
smooth-scroll on the homepage and route home + scroll from a sub-page; logo
links home. Page copy (da + en) added under COPY.pages.

apps/website/layouts/page.vue

@@ -0,0 +1,21 @@
+<script setup lang="ts">
+// Sub-page shell: same Nav + Footer chrome as the landing page, with a content
+// slot in between. Used by every footer-linked page so they share the header,
+// footer, theme and language toggle.
+import { useTheme, useLang } from '~/composables/useLanding'
+
+const t = useTheme()
+const lang = useLang()
+
+useHead({ htmlAttrs: { lang } })
+</script>
+
+<template>
+  <div :style="{ background: t.bg, color: t.fg, minHeight: '100vh', display: 'flex', flexDirection: 'column' }">
+    <LandingNav />
+    <main :style="{ flex: 1 }">
+      <slot />
+    </main>
+    <LandingFooter />
+  </div>
+</template>