feat(desktop): embed BoosAPI Desktop client as a subproject

Vendor the rebranded BoosAPI Desktop client (Tauri + Vue) into metapi as
a monorepo subdirectory under desktop/. Source only — node_modules,
dist, Cargo target and the upstream .git history are excluded.

desktop/ keeps its own independent Cargo workspace (desktop/src-tauri
with crates/*); it is not part of the backend boosapi crate, so a
`cargo check` at the metapi root still compiles only the backend. Build
the desktop app from desktop/src-tauri per desktop/README.md.

Note: app icons are still placeholder assets pending the final BoosAPI
logo. The updater signing keys live outside the repo and are not
included.

desktop/website/docs/.vitepress/theme/HomeLayout.vue

@@ -0,0 +1,51 @@
+<script setup lang="ts">
+import DefaultTheme from 'vitepress/theme';
+import { useData } from 'vitepress';
+import DownloadBar from './DownloadBar.vue';
+import ImageCarousel from './ImageCarousel.vue';
+import FeaturesGrid from './FeaturesGrid.vue';
+
+const { Layout } = DefaultTheme;
+const { frontmatter } = useData();
+</script>
+
+<template>
+  <Layout>
+    <template #home-hero-info-after>
+      <div v-if="frontmatter?.layout === 'home'" class="hero-actions-custom">
+        <DownloadBar />
+      </div>
+    </template>
+    <template #home-features-before>
+      <div v-if="frontmatter?.layout === 'home'">
+        <ImageCarousel />
+      </div>
+    </template>
+    <template #home-features-after>
+      <div v-if="frontmatter?.layout === 'home'">
+        <FeaturesGrid />
+      </div>
+    </template>
+    <template #layout-bottom>
+      <footer class="site-footer">
+        <p>© 2026 AQBot</p>
+      </footer>
+    </template>
+  </Layout>
+</template>
+
+<style scoped>
+.hero-actions-custom {
+  width: 100%;
+}
+.site-footer {
+  text-align: center;
+  padding: 24px 0;
+  color: var(--vp-c-text-3);
+  font-size: 14px;
+  border-top: 1px solid var(--vp-c-divider);
+}
+.site-footer p {
+  margin: 0;
+}
+</style>