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

backend/.env.example

@@ -1,5 +1,5 @@
 # Database Configuration
-DATABASE_URL=postgresql+psycopg://postgres:postgres@db:5432/chattermate
+DATABASE_URL=postgresql+psycopg://postgres:postgres@db:5432/replypier
 
 # CORS Configuration add backend url to allow cors from frontend
 CORS_ORIGINS=["http://localhost:3000","http://localhost:8000"]
@@ -61,7 +61,7 @@ ENVIRONMENT=development
 
 # S3 Configuration
 S3_FILE_STORAGE=false
-S3_BUCKET=chattermate-uploads
+S3_BUCKET=replypier-uploads
 S3_REGION=us-east-1
 # Leave both blank on EC2/ECS/EKS to use the attached IAM role — boto3 then
 # resolves credentials from its default chain. Set them only for static keys;