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/store/modules/notifications/helpers.js

@@ -0,0 +1,17 @@
+const INBOX_SORT_OPTIONS = {
+  newest: 'desc',
+  oldest: 'asc',
+};
+
+const sortConfig = {
+  newest: (a, b) => b.created_at - a.created_at,
+  oldest: (a, b) => a.created_at - b.created_at,
+};
+
+export const sortComparator = (a, b, sortOrder) => {
+  const sortDirection = INBOX_SORT_OPTIONS[sortOrder];
+  if (sortOrder === 'newest' || sortOrder === 'oldest') {
+    return sortConfig[sortOrder](a, b, sortDirection);
+  }
+  return 0;
+};