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

AGENT_HANDOFF.md

@@ -30,7 +30,7 @@
 | PostgreSQL 16 + pgvector | `127.0.0.1:15432` |
 | Redis | `127.0.0.1:16380` |
 
-Docker context 为 `colima-bytedesk`，Compose 项目名为 `chattermate-local`，数据库卷为 `chattermate-local_postgres_data`。它们是运行配置，不能为整理名称而改动或删除。Colima 虚拟机承载数据库与缓存，不要单独关闭。
+Docker context 为 `colima-bytedesk`，Compose 项目名为 `replypier-local`，数据库卷为 `replypier-local_postgres_data`。它们是运行配置，不能为整理名称而改动或删除。Colima 虚拟机承载数据库与缓存，不要单独关闭。
 
 ## 配置与数据保护