Vendor Chatwoot Vue 3 frontend into frontend/

Copy the Chatwoot (v4.14.0) frontend runnable subset into frontend/ for
customization:
- app/javascript/ (Vue SPA: dashboard, widget, sdk, portal, superadmin)
- app/views/ (ERB templates for vite-plugin-ruby entrypoint resolution)
- app/helpers/, app/assets/ (Rails view helpers, static assets)
- enterprise/ (Enterprise edition frontend overlay)
- config/vite.json, vite.config.ts, bin/vite (Vite-Rails toolchain)
- package.json, pnpm-lock.yaml, tailwind/postcss/eslint configs
- Gemfile, Gemfile.lock (vite_rails gem for bin/vite binstub)

Excluded Rails backend: controllers, models, services, jobs, mailers,
policies, db, lib, spec, public, node_modules.

Update references to the new frontend location:
- .gitignore: exclude frontend build artifacts (node_modules, tmp, packs),
  keep frontend/bin/ and frontend/vendor/ via negation
- backend/scripts/parity_frontend_smoke.sh: CHATWOOT_DIR default
  reference/chatwoot -> ../frontend
- backend/scripts/parity_frontend_browser_smoke.mjs: same default update
- AGENTS.md: add frontend section with Rails/Vite coupling notes
- README: architecture tree includes frontend/

frontend/app/javascript/dashboard/components-next/dropdown-menu/base/DropdownSection.vue

@@ -0,0 +1,29 @@
+<script setup>
+defineProps({
+  title: {
+    type: String,
+    default: '',
+  },
+  height: {
+    type: String,
+    default: 'max-h-96',
+  },
+});
+</script>
+
+<template>
+  <div class="-mx-2 n-dropdown-section">
+    <div
+      v-if="title"
+      class="px-4 mb-3 mt-1 leading-4 font-medium tracking-[0.2px] text-n-slate-10 text-xs"
+    >
+      {{ title }}
+    </div>
+    <ul
+      class="gap-2 grid reset-base list-none px-2 overflow-y-auto"
+      :class="height"
+    >
+      <slot />
+    </ul>
+  </div>
+</template>