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/compose.yaml

@@ -1,11 +1,11 @@
-name: chattermate-local
+name: replypier-local
 
 services:
   db:
     image: pgvector/pgvector:0.8.2-pg16
     environment:
-      POSTGRES_DB: chattermate
-      POSTGRES_USER: chattermate
+      POSTGRES_DB: replypier
+      POSTGRES_USER: replypier
       POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:?Run ./deploy/local/local.sh init first}
     ports:
       - "127.0.0.1:15432:5432"
@@ -15,7 +15,7 @@ services:
     mem_limit: 384m
     restart: unless-stopped
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U chattermate -d chattermate"]
+      test: ["CMD-SHELL", "pg_isready -U replypier -d replypier"]
       interval: 5s
       timeout: 3s
       retries: 20