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/).

package.json

@@ -0,0 +1,23 @@
+{
+  "name": "gochat",
+  "version": "0.1.0",
+  "private": true,
+  "description": "GoChat — open-source enterprise customer communication platform (Go backend + Chatwoot-derived Vue frontend)",
+  "scripts": {
+    "dev:backend": "cd backend && air -c .air.toml",
+    "dev:frontend": "cd frontend && pnpm dev",
+    "dev": "concurrently -n backend,frontend -c blue,green \"pnpm dev:backend\" \"pnpm dev:frontend\"",
+    "build:frontend": "cd frontend && pnpm build",
+    "build:sdk": "cd frontend && pnpm build:sdk",
+    "lint:frontend": "cd frontend && pnpm eslint",
+    "test:frontend": "cd frontend && pnpm test"
+  },
+  "devDependencies": {
+    "concurrently": "^9.1.0"
+  },
+  "packageManager": "pnpm@10.2.0",
+  "engines": {
+    "node": ">=20",
+    "pnpm": ">=10"
+  }
+}