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

deploy/local/demo.template.html

@@ -37,10 +37,10 @@
     <p class="note">套餐、政策与校验码均为虚构测试数据。此页面仅供本机测试；对话会调用已配置的模型 API。</p>
   </main>
   <script>
-    window.chattermateId = "__WIDGET_ID__";
-    window.chattermateBaseUrl = "http://127.0.0.1:8018/api/v1";
-    window.chattermateConfig = { position: "bottom-right" };
+    window.replypierId = "__WIDGET_ID__";
+    window.replypierBaseUrl = "http://127.0.0.1:8018/api/v1";
+    window.replypierConfig = { position: "bottom-right" };
   </script>
-  <script src="/webclient/chattermate.min.js"></script>
+  <script src="/webclient/replypier.min.js"></script>
 </body>
 </html>