Refactor docs to use Nuxt Content v3 and file-based pages

Migrates documentation from markdown-based content to Nuxt Content v3 with file-based routing. Removes old markdown content files, adds new Vue page components, updates layout and content rendering logic, introduces a Prose wrapper, and updates dependencies for Nuxt Content v3 and related packages.

docs/pages/guide/[...slug].vue

@@ -0,0 +1,18 @@
+<script setup lang="ts">
+const route = useRoute()
+
+const { data: page } = await useAsyncData(route.path, () => {
+  return queryCollection('guide').path(route.path).first()
+})
+
+useSeoMeta({
+  title: page.value?.title,
+  description: page.value?.description,
+})
+</script>
+
+<template>
+  <article>
+    <PageContent :page v-if="page" />
+  </article>
+</template>