Decouple frontend from Rails, establish pnpm workspace dev workflow

Strip the Chatwoot frontend down to a standalone Vite + Vue 3 SPA that talks
directly to the GoChat Go backend — no Ruby/Rails required.

Deleted from frontend/ (all Rails-only):
- Ruby: Gemfile, Gemfile.lock, config.ru, Capfile, Rakefile, bin/ (binstubs),
  config/ (application/boot/environment/routes/initializers/environments/locales),
  app/helpers/ (*.rb), app/views/ (ERB/jbuilder), app/assets/ (administrate scss)
- Enterprise overlay (enterprise/ — pure Ruby/jbuilder, zero JS)
- Infra: Procfile*, docker-compose*, docker/, deployment/, swagger/, .circleci/,
  .devcontainer/, .qlty/, .codegraph/, .windsurf/, .github/, .vscode/, .husky/
- Lint/config: .rubocop.yml, .scss-lint.yml, .rspec, rubocop/, .bundler-audit.yml,
  .annotaterb.yml, .all-contributorsrc, crowdin.yml, histoire.config.ts, etc.
- Stale frontend/pnpm-lock.yaml (replaced by root workspace lockfile)

Kept (frontend build essentials):
- app/javascript/ (all Vue SPA source — dashboard/widget/sdk/portal/superadmin/survey/v3)
- package.json, vite.config.ts, tailwind.config.js, postcss.config.js
- theme/, vitest.setup.js, .prettierrc

Key decoupling changes:
- vite.config.ts: removed vite-plugin-ruby, added explicit rollupOptions.input
  for all 7 entrypoints + dev-server proxy (/api,/platform,/cable,/health → GoChat)
- index.html: created static SPA entry that injects window.chatwootConfig /
  window.globalConfig (previously done by Rails ERB vueapp.html.erb)
- package.json: renamed @gochat/frontend, removed vite-plugin-ruby/histoire/husky,
  scripts now use plain vite dev/build
- tailwind.config.js: removed enterprise ERB content paths
- markdownEmbeds.js: relocated markdown_embeds.yml into app/javascript/dashboard/config/

Root pnpm workspace:
- package.json: dev:backend (air), dev:frontend (vite), dev (concurrently)
- pnpm-workspace.yaml: frontend as workspace package
- .gitignore: node_modules/, frontend/dist/, frontend build artifacts

Verified: pnpm install + vite build succeeds (4446 modules, all 7 entrypoints
produce JS+CSS chunks in dist/).

frontend/index.html

@@ -0,0 +1,57 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no, user-scalable=0" />
+    <title>GoChat</title>
+    <link rel="icon" type="image/png" href="/favicon-32x32.png" />
+    <script>
+      // GoChat frontend runtime config — injected statically (decoupled from Rails).
+      // Originally these were rendered by Rails ERB (vueapp.html.erb).
+      // Override individual keys via window.__GOCHAT_CONFIG__ before this script
+      // runs, or via VITE_* env vars at build time (see config below).
+      (function () {
+        var cfg = window.__GOCHAT_CONFIG__ || {};
+        window.chatwootConfig = Object.assign(
+          {
+            hostURL: '',                              // API base URL (empty = same origin)
+            helpCenterURL: '',
+            fbAppId: '',
+            instagramAppId: '',
+            tiktokAppId: '',
+            googleOAuthClientId: '',
+            googleOAuthCallbackUrl: '',
+            allowedLoginMethods: ['email'],
+            fbApiVersion: '',
+            whatsappAppId: '',
+            whatsappConfigurationId: '',
+            whatsappApiVersion: '',
+            signupEnabled: 'true',
+            isEnterprise: 'false',
+            isMfaEnabled: 'false',
+            inboxEventsEnabled: 'false',
+            selectedLocale: 'en',
+            enabledLanguages: [{ name: 'English', iso_639_1_code: 'en' }],
+            helpUrls: {},
+          },
+          cfg
+        );
+        window.globalConfig = Object.assign(
+          {
+            INSTALLATION_NAME: 'GoChat',
+            DISPLAY_MANIFEST: false,
+            LOGO_THUMBNAIL: '/favicon-32x32.png',
+          },
+          cfg.globalConfig || {}
+        );
+        window.errorLoggingConfig = '';
+        window.browserConfig = { browser_name: navigator.userAgent };
+      })();
+    </script>
+  </head>
+  <body class="text-slate-600">
+    <div id="app"></div>
+    <noscript id="noscript">This app works best with JavaScript enabled.</noscript>
+    <script type="module" src="/app/javascript/entrypoints/dashboard.js"></script>
+  </body>
+</html>