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/server/config.example.json

@@ -9,7 +9,7 @@
   "known_hosts": "/etc/replypier-updater/known_hosts",
   "owner_ids": ["REPLACE_WITH_DEPLOYMENT_OWNER_USER_ID"],
   "initial_revision": "REPLACE_WITH_INSTALLED_COMMIT",
-  "db_container": "chattermate-local-db-1",
-  "db_user": "chattermate",
-  "db_name": "chattermate"
+  "db_container": "replypier-local-db-1",
+  "db_user": "replypier",
+  "db_name": "replypier"
 }