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/widgets/conversation/EmptyState/EmptyStateMessage.vue

@@ -0,0 +1,33 @@
+<script>
+import FeaturePlaceholder from './FeaturePlaceholder.vue';
+export default {
+  components: { FeaturePlaceholder },
+  props: {
+    message: {
+      type: String,
+      required: true,
+    },
+  },
+};
+</script>
+
+<template>
+  <div class="flex flex-col items-center justify-center h-full">
+    <img
+      class="m-4 w-32 hidden dark:block"
+      src="dashboard/assets/images/no-chat-dark.svg"
+      alt="No Chat dark"
+    />
+    <img
+      class="m-4 w-32 block dark:hidden"
+      src="dashboard/assets/images/no-chat.svg"
+      alt="No Chat"
+    />
+    <span class="text-sm text-n-slate-12 font-medium text-center">
+      {{ message }}
+      <br />
+    </span>
+    <!-- Cmd bar, keyboard shortcuts placeholder -->
+    <FeaturePlaceholder />
+  </div>
+</template>