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/widget/helpers/specs/urlParamsHelper.spec.js

@@ -0,0 +1,51 @@
+import {
+  buildSearchParamsWithLocale,
+  getLocale,
+  buildPopoutURL,
+} from '../urlParamsHelper';
+
+describe('#buildSearchParamsWithLocale', () => {
+  it('returns correct search params', () => {
+    let windowSpy = vi.spyOn(window, 'window', 'get');
+    windowSpy.mockImplementation(() => ({
+      WOOT_WIDGET: {
+        $root: {
+          $i18n: {
+            locale: 'el',
+          },
+        },
+      },
+    }));
+    expect(buildSearchParamsWithLocale('?test=1234')).toEqual(
+      '?test=1234&locale=el'
+    );
+    expect(buildSearchParamsWithLocale('')).toEqual('?locale=el');
+    windowSpy.mockRestore();
+  });
+});
+
+describe('#getLocale', () => {
+  it('returns correct locale', () => {
+    expect(getLocale('?test=1&cw_conv=2&locale=fr')).toEqual('fr');
+    expect(getLocale('?test=1&locale=fr')).toEqual('fr');
+    expect(getLocale('?test=1&cw_conv=2&website_token=3&locale=fr')).toEqual(
+      'fr'
+    );
+    expect(getLocale('')).toEqual(null);
+  });
+});
+
+describe('#buildPopoutURL', () => {
+  it('returns popout URL', () => {
+    expect(
+      buildPopoutURL({
+        origin: 'https://chatwoot.com',
+        conversationCookie: 'random-jwt-token',
+        websiteToken: 'random-website-token',
+        locale: 'ar',
+      })
+    ).toEqual(
+      'https://chatwoot.com/widget?cw_conversation=random-jwt-token&website_token=random-website-token&locale=ar'
+    );
+  });
+});