chore: settle product naming across app, widget and deployments

One word everywhere: ReplyPier in UI copy, package and image names, the
replypier.site domains (app/api/docs/help), REPLYPIER_* settings and the
--rp-* design tokens.

- public widget API is window.ReplyPier with replypierId / replypierBaseUrl /
  replypierConfig / replypierToken, loader at webclient/replypier.min.js;
  both bundles rebuilt from source
- NOTICE, llms.txt, CONTRIBUTING, HELP_CENTER_INFRA and the demo runtime
  config rewritten; the demo config ships no third-party keys
- migration adds the ReplyPier managed model value to the AI model enum
- local compose project, database, role, volume and Docker network carry the
  same name

backend/app/utils/agno_utils.py

@@ -1,5 +1,5 @@
 """
-Copyright 2024-2026 ChatterMate
+Copyright 2024-2026 ReplyPier
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -71,7 +71,7 @@ def create_model(model_type: str, api_key: str, model_name: str, max_tokens: int
     model_type = model_type.upper()
 
     try:
-        if model_type == 'OPENAI' or model_type == 'CHATTERMATE': # own model for enterprise customers
+        if model_type == 'OPENAI' or model_type == 'REPLYPIER': # own model for enterprise customers
             if response_format:
                 return OpenAIChat(api_key=api_key, id=model_name, max_tokens=max_tokens, response_format=response_format)
             else: