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/api/agent.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.
@@ -723,23 +723,23 @@ async def generate_instructions(
         except ImportError:
             HAS_ENTERPRISE = False
         
-        # Get API key and model - first check for ChatterMate config if enterprise is available
+        # Get API key and model - first check for ReplyPier config if enterprise is available
         api_key = ""
         model_name = ""
         model_type = ""
         base_url = None
 
         if HAS_ENTERPRISE:
-            # Use Groq/OpenAI with keys from env for ChatterMate model
+            # Use Groq/OpenAI with keys from env for ReplyPier model
             model_type = 'OPENAI'
-            model_name = os.getenv('CHATTERMATE_MODEL_NAME', 'gpt-4o-mini')
-            api_key = os.getenv('CHATTERMATE_API_KEY', '')
+            model_name = os.getenv('REPLYPIER_MODEL_NAME', 'gpt-4o-mini')
+            api_key = os.getenv('REPLYPIER_API_KEY', '')
             
             if not api_key:
-                logger.error("ChatterMate API key not found in environment")
+                logger.error("ReplyPier API key not found in environment")
                 raise HTTPException(
                     status_code=500,
-                    detail="ChatterMate API configuration missing"
+                    detail="ReplyPier API configuration missing"
                 )
         else:
             # Get from organization's AI config