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/src/components/WorkGroupsSection.vue

@@ -0,0 +1,55 @@
+<script setup lang="ts">
+import { useI18n } from 'vue-i18n';
+const { t } = useI18n();
+</script>
+
+<template>
+  <section class="mx-auto max-w-[1200px] scroll-mt-[84px] px-6 py-[92px]">
+    <div
+      v-reveal
+      class="flex flex-wrap items-center gap-12 rounded-[18px] border border-zinc-800 p-[clamp(28px,4vw,52px)]"
+      style="background: linear-gradient(180deg, rgba(24, 24, 27, 0.55), rgba(12, 12, 14, 0.55))"
+    >
+      <div class="min-w-[280px] flex-[1_1_360px]">
+        <div class="mb-3 font-mono text-xs uppercase tracking-[0.12em] text-emerald-400">{{ t('grpKicker') }}</div>
+        <h2 class="m-0 mb-4 text-[clamp(26px,3vw,36px)] font-semibold leading-[1.15] tracking-[-0.025em] text-zinc-50">
+          {{ t('grpTitle') }}
+        </h2>
+        <p class="m-0 text-[16.5px] leading-[1.6] text-zinc-400">{{ t('grpBody') }}</p>
+      </div>
+      <div class="flex min-w-[280px] flex-[1_1_360px] justify-center">
+        <div class="flex w-full max-w-[380px] items-center">
+          <div class="flex flex-none flex-col items-center gap-2">
+            <div
+              class="inline-flex h-[62px] w-[62px] items-center justify-center rounded-[15px] border border-emerald-500/35 bg-emerald-500/[0.12] text-emerald-400"
+            >
+              <svg width="26" height="26" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.7" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M2.97 12.92A2 2 0 0 0 2 14.63v3.24a2 2 0 0 0 .97 1.71l3 1.8a2 2 0 0 0 2.06 0L12 19v-5.5l-5-3-4.03 2.42Z" /><path d="M7 16.5 12 13.5" /><path d="M12 13.5V19l3.97 2.38a2 2 0 0 0 2.06 0l3-1.8a2 2 0 0 0 .97-1.71v-3.24a2 2 0 0 0-.97-1.71L17 10.5l-5 3Z" /><path d="m17 16.5 4.74-2.85" /><path d="M7.97 4.42A2 2 0 0 0 7 6.13v4.37l5 3 5-3V6.13a2 2 0 0 0-.97-1.71l-3-1.8a2 2 0 0 0-2.06 0z" /></svg>
+            </div>
+            <span class="font-mono text-[11px] text-zinc-300">payments</span>
+          </div>
+          <div class="relative h-[96px] flex-1">
+            <svg width="100%" height="100%" viewBox="0 0 100 96" preserveAspectRatio="none" class="absolute inset-0" aria-hidden="true">
+              <path d="M0 48 H40 V14 H100" fill="none" stroke="rgba(16,185,129,.45)" stroke-width="1.4" />
+              <path d="M0 48 H40 V48 H100" fill="none" stroke="rgba(16,185,129,.45)" stroke-width="1.4" />
+              <path d="M0 48 H40 V82 H100" fill="none" stroke="rgba(16,185,129,.45)" stroke-width="1.4" />
+            </svg>
+          </div>
+          <div class="flex flex-none flex-col gap-2.5">
+            <div class="flex items-center gap-2 rounded-lg border border-zinc-800 bg-[#0c0c0e] px-3 py-2">
+              <span class="h-1.5 w-1.5 rounded-full bg-sky-300"></span>
+              <span class="font-mono text-[11px] text-zinc-300">api</span>
+            </div>
+            <div class="flex items-center gap-2 rounded-lg border border-zinc-800 bg-[#0c0c0e] px-3 py-2">
+              <span class="h-1.5 w-1.5 rounded-full bg-sky-300"></span>
+              <span class="font-mono text-[11px] text-zinc-300">web</span>
+            </div>
+            <div class="flex items-center gap-2 rounded-lg border border-zinc-800 bg-[#0c0c0e] px-3 py-2">
+              <span class="h-1.5 w-1.5 rounded-full bg-sky-300"></span>
+              <span class="font-mono text-[11px] text-zinc-300">sdk</span>
+            </div>
+          </div>
+        </div>
+      </div>
+    </div>
+  </section>
+</template>