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/shared/components/DateSeparator.vue

@@ -0,0 +1,29 @@
+<script>
+import { formatDate } from 'shared/helpers/DateHelper';
+
+export default {
+  props: {
+    date: {
+      type: String,
+      required: true,
+    },
+  },
+  computed: {
+    formattedDate() {
+      return formatDate({
+        date: this.date,
+        todayText: this.$t('TODAY'),
+        yesterdayText: this.$t('YESTERDAY'),
+      });
+    },
+  },
+};
+</script>
+
+<template>
+  <div
+    class="text-sm text-n-slate-11 h-[50px] leading-[50px] relative text-center w-full before:content-[''] before:h-px before:absolute before:top-6 before:w-[calc((100%-120px)/2)] before:bg-n-slate-4 before:dark:bg-n-slate-6 before:left-0 after:content-[''] after:h-px after:absolute after:top-6 after:w-[calc((100%-120px)/2)] after:bg-n-slate-4 after:dark:bg-n-slate-6 after:right-0"
+  >
+    {{ formattedDate }}
+  </div>
+</template>