chore(brand): rename the product to ReplyPier

The upstream project name is gone from code, assets, docs and build
output: brand strings, domains (replypier.site and its app/api/docs/help
subdomains), env prefixes, image and network names, the widget's public
JS API (window.ReplyPier, replypierId/BaseUrl/Config/Token), CSS tokens
(--rp-*), file and directory names, and the WordPress plugin package.

- widget loader is now webclient/replypier.min.js; both bundles rebuilt
  from source (backend/assets/widget.{js,css}, frontend/public/webclient)
- NOTICE, llms.txt, CONTRIBUTING, HELP_CENTER_INFRA and config.dev.js
  rewritten rather than string-swapped; the demo config no longer ships
  the previous vendor's Firebase/Razorpay/Google keys
- new migration replypier_ai_model_001 adds REPLYPIER to the managed
  AIModelType and rewrites pre-rename rows
- local compose project, database, role and volume renamed; LOCAL_DEPLOY
  documents carrying the old local data over

frontend/index.html

@@ -19,7 +19,7 @@
        and src/config/themeColors.ts — a static document cannot import them. */
     (function () {
       try {
-        var stored = localStorage.getItem('cm-theme') || 'light';
+        var stored = localStorage.getItem('rp-theme') || 'light';
         var resolved = stored === 'system'
           ? (window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light')
           : (stored === 'light' ? 'light' : 'dark');