Enable beta auto-deploy + Tianji beta ID / consent-gated events (#35) (#42)

## Summary

Closes #35.

- **Flip deploy workflows** (mirror `dta_webapp`): push/merge to `master` → auto-deploy **beta**; **Deploy Prod** is `workflow_dispatch` only
- **Tianji**: `REACT_APP_TIANJI_WEBSITE_ID` + `REACT_APP_DEPLOY_ENV` in `.env.production` / `.env.beta`; Tracker loads page views always on prod/beta
- **Consent policy**: page views always live; custom events / identify gated via `analyticsConsent` + `AnalyticsConsentBanner` + `trackEvent`/`identifyUser` helpers (call sites remain #36)
- Remove invalid Tianji `<script>` from `index.tsx` (Tracker component owns injection)
- README documents beta auto / prod button + Tianji policy

## Ops note — beta Tianji website ID

Prod ID unchanged: `cm7x7m52m03kbddswbswrt17y`.

`.env.beta` has `REACT_APP_TIANJI_WEBSITE_ID=` empty until a **Hesychia Beta** website is created in Tianji (workspace `cm7w8087y020lddswyhamadj2`). Paste the new id into `.env.beta` before beta page views show under a distinct site.

## Test plan

- [x] `npm run test:ci` (106 tests)
- [ ] Create Hesychia Beta Tianji website; set `REACT_APP_TIANJI_WEBSITE_ID` in `.env.beta`
- [ ] Merge to master → Deploy Beta runs; prod does **not** auto-deploy
- [ ] Manual Run workflow on Deploy Prod still works
- [ ] Beta build hits `beta.chatbackend` REST/WS; static root `/var/www/beta.chat.aimloperations/html` (8083)
- [ ] Prod/beta: tracker.js loads without accepting consent; banner shows until Accept/Decline; `trackEvent` only fires after AcceptReviewed-on: #42

llm-fe/.env.production

@@ -1,4 +1,7 @@
 # Production API hosts (current). Target public product domain: hesychia.ai
 # Flip these to hesychia.ai API hosts when server-infra / DNS cut over.
+REACT_APP_DEPLOY_ENV=production
 REACT_APP_BACKEND_REST_API_BASE_URL=https://chatbackend.aimloperations.com/api/
 REACT_APP_BACKEND_WS_API_BASE_URL=wss://chatbackend.aimloperations.com/ws/chat_again/
+# Tianji website id (prod). Page views always on; custom events need consent.
+REACT_APP_TIANJI_WEBSITE_ID=cm7x7m52m03kbddswbswrt17y