feat: Add packages/site — landing vitrine (Vue 3 + Tailwind 4)

- Scaffold packages/site with 11 Vue components: hero (animated terminal), features, showcase, work groups, how-it-works, security, FAQ accordion, footer
- i18n EN/FR via vue-i18n with 82+ keys, autodetect navigator.language, toggle without reload
- Animated timeline (terminal, dialog, toast) ported from design, scroll-reveal, copy buttons (2 instances)
- Self-hosted JetBrains Mono fonts (@fontsource), optimized assets (mark 28KB, og-cover 1200×630)
- SEO: canonical, og:image, theme-color, robots.txt, sitemap.xml for git-arboretum.com
- Monorepo integration (decoupled from npm release): build:site / dev:site / preview:site scripts
- CI: add build:site step to ci.yml for early detection; create .gitea/workflows/prod.yml for FTPS deploy (lftp mirror) to git-arboretum.com
- Validated builds ✓ and UI rendering (EN/FR headless test) ✓

packages/site/vite.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig } from 'vite';
+import vue from '@vitejs/plugin-vue';
+import tailwindcss from '@tailwindcss/vite';
+
+// Site vitrine statique (git-arboretum.com) : aucune dépendance au daemon, donc
+// pas de proxy /api /ws (contrairement à packages/web). `base: '/'` car servi
+// à la racine d'un domaine dédié.
+export default defineConfig({
+  plugins: [vue(), tailwindcss()],
+  base: '/',
+  build: {
+    outDir: 'dist',
+    target: 'es2020',
+  },
+});