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/package.json

@@ -0,0 +1,24 @@
+{
+  "name": "@arboretum/site",
+  "private": true,
+  "version": "0.1.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vue-tsc --noEmit && vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "vue": "^3.5.38",
+    "vue-i18n": "^11.4.5"
+  },
+  "devDependencies": {
+    "@fontsource/jetbrains-mono": "^5.1.0",
+    "@tailwindcss/vite": "^4.3.0",
+    "@vitejs/plugin-vue": "^6.0.7",
+    "tailwindcss": "^4.3.0",
+    "typescript": "^5.7.0",
+    "vite": "^8.0.16",
+    "vue-tsc": "^3.3.4"
+  }
+}